Systems and methods for waste treatment

ABSTRACT

Systems and methods for aerobically processing waste, in which an aerobic bioreactor is in selective fluid communication with a source of oxygen-rich liquid medium. The aerobic bioreactor is configured for aerobically processing waste via bacteria fixed on media to provide processed effluent from the waste. The source of oxygen-rich liquid medium is different from the aerobic bioreactor.

TECHNOLOGICAL FIELD

The presently disclosed subject matter relates to methods and systemsfor waste treatment, in particular for waste water treatment.

PRIOR ART

References considered to be relevant as background to the presentlydisclosed subject matter are listed below:

-   U.S. Pat. No. 6,896,804-   U.S. Pat. No. 4,005,546-   U.S. Pat. No. 4,209,388-   U.S. Pat. No. 3,955,318-   US 2010/288695A-   JP 63252596A-   US 2011/151547A-   US 2003/209489A-   JP 3198727A-   JP 61197098A-   JP 58166989A-   FR 2344627A-   CN 2018014190-   CN 101853955A-   WO 11022754A-   US 2010/300962A-   CN 101560484A-   JP 2008272721A-   US 2010/018918-   CN 102211834-   Gonzalez C. Marciniak J, Viliaverde S, León C, García P A, Muñoz R.,    Water Science and Technology, 58; 92-105; 2008.-   Muñoz R, Guieysse B., Water Research, 40; 2799-2815 2006

Acknowledgement of the above references herein is not to be inferred asmeaning that these are in any way relevant to the patentability of thepresently disclosed subject matter.

BACKGROUND

The desirability of treating waste particularly in liquid form, alsoreferred to herein interchangeably as wastewater, is well known. Sometypes of waste treatment are conventionally based on biologicaloxidation of the organic matter in the waste to carbon dioxide (CO₂),using microorganisms such as bacteria. Many such waste treatmentprocesses occur in the presence of oxygen, referred to as aerobicprocesses.

By way of non-limiting example, U.S. Pat. No. 6,896,804 discloses asystem and a method for aerobic treatment of waste, including thecontinual introduction of microalgae.

Also by way of non-limiting example: U.S. Pat. No. 4,005,546 discloses amethod of waste treatment and algae recovery; U.S. Pat. No. 4,209,388discloses a method for the treatment of sanitary sewage comprising watercontaining suspended or dissolved organic matter, the concentration ofwhich is measured by biochemical oxygen demand (BOD); U.S. Pat. No.3,955,318 discloses a method of producing an algae product and ofpurifying aqueous organic waste material to provide clean water.

GENERAL DESCRIPTION

According to a first aspect of the presently disclosed subject matter,there is provided a system for aerobically processing waste, inparticular liquid waste, for example waste water, comprising:

-   -   an aerobic bioreactor configured for aerobically processing the        waste via bacteria fixed on media to provide processed effluent        from the waste;    -   a source of oxygen-rich liquid medium, said source being        different from and/or separate from said aerobic bioreactor,        said source being in selective fluid communication with said        aerobic bioreactor.

The system can comprise a recirculation circuit configured forcontrollably recirculating said liquid medium between said aerobicbioreactor and said source.

Additionally or alternatively, said system is configured for preventingthe media from being transferred from the aerobic bioreactor to saidsource.

Additionally or alternatively, said media is restricted to a confinedvolume within said aerobic bioreactor.

Additionally or alternatively, in operation of the system a flow of saidoxygen-rich liquid medium is forced through (i.e., into and out of) saidconfined volume wherein to interact with said bacteria.

According to a second aspect of the presently disclosed subject matter,there is provided a system for aerobically processing waste, comprising:

-   -   an aerobic bioreactor configured for aerobically processing        waste to provide processed effluent from the waste;    -   a source of oxygen-rich liquid medium, said source being        different from and/or separate from the bioreactor,    -   a recirculation circuit configured for controllably        recirculating said liquid medium between said aerobic bioreactor        and said source.

The aerobic bioreactor can be configured for aerobically processingwaste via bacteria fixed on media, and optionally said system can beconfigured for preventing the media from being transferred from theaerobic bioreactor to the source. Additionally or alternatively, saidmedia is restricted to a confined volume within said aerobic bioreactor.In operation of the system a flow of said oxygen-rich liquid medium isforced through (i.e., into and out of) said confined volume wherein tointeract with said bacteria.

According to a third aspect of the presently disclosed subject matter,there is provided a system for aerobically processing waste, comprising:

-   -   bacteria for aerobically processing waste to provide processed        effluent from the waste, said bacteria being fixed on media        restricted to a confined volume;    -   a flow of oxygen-rich liquid medium forced through (i.e., into        and out of) said confined volume wherein to interact with said        bacteria.

Said confined volume is provided in an aerobic bioreactor, and a sourceof oxygen-rich liquid medium provides said flow of oxygen-rich medium,said source being different from and/or separate from the aerobicbioreactor.

Additionally or alternatively, said system is configured for preventingthe media from being transferred from the aerobic bioreactor to thesource.

Additionally or alternatively, the system comprises a recirculationcircuit configured for controllably recirculating said liquid mediumbetween said aerobic bioreactor and said source.

In the system according to any one of the aforementioned first, secondand third aspects of the presently disclosed subject matter, said sourcecomprises photosynthetic microorganisms that generate oxygen to saidliquid medium responsive to exposure to light.

Additionally or alternatively, said source comprises any one ofphotosynthetic eukaryotic microorganisms and photosynthetic prokaryoticmicroorganisms that generate oxygen to said liquid medium responsive toexposure to light.

Additionally or alternatively, said source comprises algae that generateoxygen to said liquid medium responsive to exposure to light.

For example, said photosynthetic microorganisms comprise at least oneof: Chlorella spp, spirulina, scendesmus, or any other type ofphotosynthetic microalgae or cyanobacteria.

Additionally or alternatively, said source comprises a reservoircomprising a channel therein defining a reservoir internal volume, andconfigured for driving said liquid medium around said channel inoperation of the system.

Additionally or alternatively, the system according to any one of theaforementioned first, second and third aspects of the presentlydisclosed subject matter, further comprises an auxiliary aerationsystem, configured for selectively providing gaseous oxygen or air tosaid bioreactor.

Additionally or alternatively, the system according to any one of theaforementioned first, second and third aspects of the presentlydisclosed subject matter, further comprises an auxiliary CO₂ system,configured for selectively providing carbon dioxide to said source.

Additionally or alternatively, said media is fixed in situ within thebioreactor, for example in the form of fixed media. For example themedia comprises a substrate that is fixed on one or more sides thereofto the structure of the aerobic bioreactor. For example, such fixedmedia can be in the form of a plastic matrix attached to the floor orsides of the aerobic bioreactor and/or ropes or fibers hanging withinthe liquid in the aerobic bioreactor and attached either to the walls orother structure of the aerobic bioreactor or attached to a rigid framelocated within the aerobic bioreactor.

Additionally or alternatively, said media is mobile, i.e., free-floatingwithin the bioreactor.

Additionally or alternatively, said media comprise biofilm carrierelements, in the form of solid inert substrates having a relativelylarge surface area to volume ratio. Such substrates can include, forexample, any one of polyethylene or other plastics, and the respectivesurface area to volume ratio can be, for example, between about 500m²/m³ and about 1300 m²/m³, for example about 650 m²/m³. Alternatively,substrates can include, for example, any one of metallic materials,fibers, cloths, mineral materials (such as for example carbon, volcanictuff, gravel), and so on, at least some of which can have respectivesurface area to volume ratios much higher than 1300 m²/m³.

Additionally or alternatively, the system according to any one of theaforementioned first, second and third aspects of the presentlydisclosed subject matter, further comprises a waste inlet configured forreceiving the waste and a dispensing outlet for dispensing treatedeffluent, and wherein

-   -   said bioreactor comprises at least one vessel defining a        respective aerobic processing volume, the at least one vessel        comprising a bioreactor fluid medium inlet and a bioreactor        fluid medium outlet, each in selective fluid communication with        said source, the at least one vessel being configured for        ensuring that the respective aerobic processing volume is        partially or fully shielded from light at least during operation        of the system;    -   said source comprises at least one reservoir defining a        respective reservoir volume for accommodating a volume of said        liquid medium, and further comprising a source fluid medium        inlet and a source fluid medium outlet, each in selective fluid        communication with said aerobic bioreactor, and a driving device        for providing motion to said liquid medium within said        respective reservoir volume, the at least one reservoir being        configured for ensuring that the respective reservoir volume is        exposed to light at least during operation of said source        wherein to provide said oxygen-rich liquid medium.

For example, said driving device comprises a powered paddling devicemounted to the respective said reservoir. Additionally or alternatively,said at least one reservoir comprises at least one flow channel in theform of a horizontal endless loop. For example, said at least one flowchannel has an annular plan form. For example, said at least one flowchannel has a raceway configuration. Additionally or alternatively, saidsource fluid medium outlet is configured for preventing outflow of saidmedia therethrough.

Additionally or alternatively, the system according to any one of theaforementioned first, second and third aspects of the presentlydisclosed subject matter further comprises:

-   -   at least one set of conduits providing said fluid communication        between said at least one said vessel and a respective said        reservoir;    -   a pumping system, different from said driving device, for        providing recirculation of said medium between said at least one        vessel and the respective said reservoir through said set of        conduits.

For example, one said conduit connects said source fluid medium inletwith said bioreactor fluid medium outlet and wherein another saidconduit connects said source fluid medium outlet with said bioreactorfluid medium inlet.

For example, said bioreactor is configured for providing a through-flowof at least the oxygen-rich liquid medium through the bioreactor at apredetermined velocity, wherein said predetermined velocity issufficient to cause the media therein to expand within the bioreactorand to mix therein with at least the oxygen-rich liquid medium.

According to a fourth aspect of the presently disclosed subject matter,there is provided a method for aerobically processing waste, comprising:

-   -   aerobically reacting waste in an aerobic bioreactor via bacteria        fixed on media;    -   providing oxygen-rich liquid medium to the bioreactor from an        oxygen-rich liquid source, wherein the oxygen-rich liquid source        is different from and/or separate from the bioreactor.

For example, the method further comprises controllably recirculatingsaid liquid medium between said aerobic bioreactor and said oxygen-richsource.

Additionally or alternatively, the method comprises preventing the mediafrom being transferred from the aerobic bioreactor to said source.

Additionally or alternatively, said media is restricted to a confinedvolume within said aerobic bioreactor. For example, a flow of saidoxygen-rich liquid medium is forced through said confined volume whereinto interact with said bacteria.

According to a fifth aspect of the presently disclosed subject matter,there is provided a method for aerobically processing waste, comprising:

-   -   aerobically processing waste in an aerobic bioreactor to provide        processed effluent from the waste;    -   providing oxygen-rich liquid medium to the bioreactor from an        oxygen-rich liquid source, wherein the oxygen-rich liquid source        is different from and/or separate from the bioreactor,    -   controllably recirculating said liquid medium between said        aerobic bioreactor and said source.

For example, said aerobic bioreactor is configured for aerobicallyprocessing waste via bacteria fixed on media.

For example, the method further comprises preventing the media frombeing transferred from the aerobic bioreactor to the oxygen-rich liquidsource.

Additionally or alternatively, said media is restricted to a confinedvolume within said aerobic bioreactor. For example, a flow of saidoxygen-rich liquid medium is forced through said confined volume whereinto interact with said bacteria.

According to a sixth aspect of the presently disclosed subject matter,there is provided a method for aerobically processing waste, comprising:

-   -   aerobically processing waste with bacteria to provide processed        effluent from the waste, said bacteria being fixed on media        restricted to a confined volume;    -   forcing a flow of oxygen-rich liquid medium through (i.e., into        and out of) said confined volume wherein to interact with said        bacteria.

For example, said confined volume is provided in an aerobic bioreactor,and wherein a source of oxygen-rich liquid medium provides said flow ofoxygen-rich medium, said source being different from the aerobicbioreactor.

For example, the method comprises preventing the media from beingtransferred from the aerobic bioreactor to the source. Additionally oralternatively, the method comprises controllably recirculating saidliquid medium between said aerobic bioreactor and said source.

In the method according to any one of the aforementioned fourth, fifth,and sixth aspects of the presently disclosed subject matter, said liquidmedium contains photosynthetic microorganisms that generate and provideoxygen to said liquid medium responsive to exposure to light.

According to a seventh aspect of the presently disclosed subject matter,there is provided a method for aerobically processing waste, comprising:

-   -   reacting waste aerobically with bacteria in a bioreactor volume        under conditions configured for inhibiting or reducing growth of        photosynthetic microorganisms;    -   providing a flow of oxygen-producing photosynthetic        microorganisms through the bioreactor volume from a source        configured for promoting oxygen production by photosynthetic        microorganisms, the source being different from and/or separate        from the bioreactor volume, the photosynthetic microorganisms        generating and providing oxygen to said liquid medium responsive        to exposure to light; and    -   preventing at least a majority of the bacteria from exiting the        bioreactor with said flow of photosynthetic microorganisms.

According to an eighth aspect of the presently disclosed subject matter,there is provided a method for aerobically processing waste, comprising:

-   -   reacting waste aerobically with bacteria in a bioreactor volume        under conditions configured for inhibiting or reducing growth of        photosynthetic microorganisms;    -   providing a flow of oxygen-rich liquid which optionally contains        oxygen-producing photosynthetic microorganisms through the        bioreactor volume from a source configured for promoting oxygen        production by photosynthetic microorganisms, the source being        different from and/or separate from the bioreactor volume, the        photosynthetic microorganisms in the liquid medium generating        and providing oxygen to said liquid medium responsive to        exposure to light; and    -   preventing at least a majority of the bacteria from exiting the        bioreactor with said flow of liquid that contains photosynthetic        microorganisms or that contains oxygen produced by these        organisms.

In the method according to any one of the aforementioned fourth, fifth,sixth, seventh and eighth aspects of the presently disclosed subjectmatter, said photosynthetic microorganisms comprise any one ofphotosynthetic eukaryotic microorganisms and photosynthetic prokaryoticmicroorganisms that generate oxygen to said liquid medium responsive toexposure to light. Additionally or alternatively, said source comprisesalgae that generate oxygen to said liquid medium responsive to exposureto light. Additionally or alternatively, said photosyntheticmicroorganisms comprise at least one of: Chlorella spp, spirulina,scendesmus, or any other type of micro algae or cyanobacteria.

In the system according to any one of the aforementioned first, secondand third aspects of the presently disclosed subject matter, and/or inthe method according to any one of the aforementioned fourth, fifth,sixth, seventh or eighth aspects of the presently disclosed subjectmatter, the waste is aerobically treatable for removing pollutantstherefrom. For example, said waste is a liquid waste. For example, saidwaste comprises waste water. For example, said waste includes organictypes of waste. For example, said waste comprises at least one ofanimal, agricultural, industrial or human waste transported in water oranother liquid medium.

In the method according to any one of the aforementioned fourth, fifth,sixth, seventh and eighth aspects of the presently disclosed subjectmatter, the method can further comprise at least one of:

-   -   selectively providing gaseous oxygen or air to said bioreactor;        and    -   selectively providing carbon dioxide to said source.

Additionally or alternatively, a portion of said media is fixed in situwithin the bioreactor.

Additionally or alternatively, at least a portion of said media ismobile within the bioreactor.

Additionally or alternatively, said media comprise biofilm carrierelements, in the form of solid inert substrates having a relativelylarge surface area to volume ratio.

Additionally or alternatively, the method comprises:

-   -   partially or fully shielding the respective aerobic processing        volume from light;    -   ensuring that the respective reservoir volume is exposed to        light.

Additionally or alternatively, the step of aerobically reacting wasteincludes providing a through-flow of at least the oxygen-rich liquidmedium through the bioreactor at a predetermined velocity, wherein saidpredetermined velocity is sufficient to cause the media therein toexpand and to mix therein with at least the oxygen-rich liquid medium.

For example, said method is performed in batch mode or said method isperformed in continuous flow mode.

According to a ninth aspect of the presently disclosed subject matter,there is provided an aerobic bioreactor configured for aerobicallyprocessing waste via bacteria fixed on media that are mobile within theaerobic bioreactor to provide processed effluent from the waste,comprising:

-   -   a reaction vessel having a fluid inlet and a fluid outlet, and a        waste inlet, and defining an internal volume;    -   said waste inlet being configured for selectively providing        waste to said aerobic bioreactor;    -   said fluid inlet and said fluid outlet being connectable to a        source of oxygen-rich liquid medium, the source being different        from said aerobic bioreactor, wherein said source is in        selective fluid communication with said aerobic bioreactor via        said fluid inlet and said fluid outlet to provide a        recirculation circuit configured for controllably recirculating        at least the liquid medium between said aerobic bioreactor and        the source;    -   the reaction vessel being configured for providing, via said        recirculation circuit, a through-flow of at least the        oxygen-rich liquid medium through said internal volume at a        predetermined velocity, wherein said predetermined velocity is        sufficient to cause the media to expand within the reaction        vessel and mix therein with at least the oxygen-rich liquid        medium.

For example, said predetermined velocity is sufficient to provide afluidized bed effect to the media within said reaction vessel.

In at least a first example, at said predetermined velocity issufficient to provide upward motion to at least a first proportion ofsaid media having a density greater than that of said liquid medium. Forexample, said flow velocity within said reaction vessel is in adirection generally opposed to the gravitational gradient. For examplesaid first proportion is a majority (for example over 50%) of the totalamount of said media in said reaction vessel. For example said firstproportion is less than 50% of the total amount of said media in saidreaction vessel. For example, said fluid inlet is provided at a lowerpart of the reaction vessel and said fluid outlet is provided at anupper part of the reaction vessel. For example, said fluid inletcomprises a plurality of openings within said reaction vessel, andwherein said openings are distributed over a bottom base of the reactionvessel providing a desired coverage with respect to the bottom base. Forexample, said openings are uniformly distributed over a bottom base ofthe reaction vessel providing a full coverage with respect to the bottombase. For example, said reaction vessel comprises one or more drafttubes, each draft tube being configured to further increase said fluidvelocity therein. For example, each said draft tube provides aninitially decreasing flow area in the direction of flow therethrough.For example, said openings of said fluid inlet are uniformly distributedover a part of bottom base of the reaction vessel opposite said drafttubes providing a full coverage with respect to the draft tubes.

In at least a first example, at said predetermined velocity issufficient to provide downward motion to said media having a densityless than that of said liquid medium. For example, said flow velocitywithin said reaction vessel is in at least partially aligned with thegravitational gradient, and wherein at least a second proportion of saidmedia has a density less than that of said liquid medium. For example,said second proportion is a majority of the total amount of said mediain said reaction vessel. For example, said fluid inlet is provided at anupper part of the reaction vessel. For example, said reaction vesselcomprises one or more draft tubes, each draft tube being configured tofurther increase said fluid velocity therein. For example, said openingsof said fluid inlet are uniformly distributed over an upper opening ofeach said draft tubes providing a full coverage with respect to thedraft tubes. For example, each said draft tube provides an initiallydecreasing flow area in the direction of flow therethrough.

The aerobic bioreactor according to the ninth aspect of the presentlydisclosed subject matter can optionally further comprise a first sludgereceiving receptacle at a lower part thereof for receiving and disposingof sludge from the aerobic bioreactor.

Additionally or alternatively, the aerobic bioreactor further comprisesa clarifying vessel on an upper part of said reaction vessel and influid communication therewith, wherein said fluid outlet is provided onsaid clarifying vessel, and wherein said clarifying vessel is configuredfor reducing said fluid velocity therein. For example, said clarifyingvessel comprises a cross-sectional area that increases in an upwarddirection. For example, said clarifying vessel comprises a second sludgereceiving receptacle at a lower part thereof for receiving and disposingof sludge from the clarifying vessel.

The aerobic bioreactor according to the ninth aspect of the presentlydisclosed subject matter can optionally further comprise an effluentoutlet for removing processed effluent from said aerobic bioreactor.

According to a tenth aspect of the presently disclosed subject matter,there is provided a system for processing waste, comprising:

-   -   an aerobic bioreactor as defined above regarding the ninth        aspect of the presently disclosed subject matter;    -   the source of oxygen-rich liquid medium as defined above        regarding the ninth aspect of the presently disclosed subject        matter, wherein said fluid inlet and said fluid outlet are        connected to the source of oxygen-rich liquid medium; and    -   the media as defined above regarding the ninth aspect of the        presently disclosed subject matter, and provided in said aerobic        bioreactor.

For example, the system according to the tenth aspect of the presentlydisclosed subject matter said system is configured for preventing themedia from being transferred from the aerobic bioreactor to said source.

Additionally or alternatively, said media is restricted to a confinedvolume within said aerobic bioreactor.

Additionally or alternatively, said source comprises photosyntheticmicroorganisms that generate oxygen to said liquid medium responsive toexposure to light.

Additionally or alternatively, said source comprises any one ofphotosynthetic eukaryotic microorganisms and photosynthetic prokaryoticmicroorganisms that generate oxygen to said liquid medium responsive toexposure to light.

Additionally or alternatively, said source comprises algae that generateoxygen to said liquid medium responsive to exposure to light.

Additionally or alternatively, wherein said photosyntheticmicroorganisms comprise at least one of: Chlorella spp, spirulina,scendesmus, or any other photosynthetic microalgae or cyanobacteria.

Additionally or alternatively, said source comprises a reservoircomprising a channel therein defining a reservoir internal volume, andconfigured for driving said liquid medium around said channel inoperation of the system.

Additionally or alternatively, the system further comprises an auxiliaryaeration system, configured for selectively providing gaseous oxygen orair to said bioreactor.

Additionally or alternatively, the system further comprises an auxiliaryCO₂ system, configured for selectively providing carbon dioxide to saidsource.

Additionally or alternatively, a portion of said media is fixed in situwithin the bioreactor.

For example, said media comprise biofilm carrier elements, in the formof solid inert substrates having a relatively large surface area tovolume ratio.

Additionally or alternatively, the system comprises a waste inletconfigured for receiving the waste and a dispensing outlet fordispensing treated effluent, and wherein:

-   -   said internal volume is partially or fully shielded from light        at least during operation of the system;    -   said source comprises at least one reservoir defining a        respective reservoir volume for accommodating a volume of said        liquid medium, and further comprising a source fluid medium        inlet and a source fluid medium outlet, each in selective fluid        communication with said aerobic bioreactor, and a driving device        for providing motion to said liquid medium within said        respective reservoir volume, the at least one reservoir being        configured for ensuring that the respective reservoir volume is        exposed to light at least during operation of said source        wherein to provide said oxygen-rich liquid medium.

For example, said driving device comprises a powered paddling devicemounted to the respective said reservoir. For example, said at least onereservoir comprises at least one flow channel in the form of ahorizontal endless loop. For example, said at least one flow channel hasan annular plan form. For example, said source fluid medium outlet isconfigured for preventing outflow of said media therethrough.

For example, the system comprises:

-   -   at least one set of conduits providing said fluid communication        between said at least one said vessel and a respective said        reservoir;    -   a pumping system, different from said driving device, for        providing recirculation of said medium between said at least one        vessel and the respective said reservoir through said set of        conduits.

For example, said waste is aerobically treatable for removing pollutantstherefrom. For example, said waste is a liquid waste. For example, saidwaste comprises at least one of waste water; organic types of waste; atleast one of animal, agricultural, industrial or human waste transportedin water or another liquid medium.

According to other aspects of the presently disclosed subject matterthere are provided systems and methods for aerobically processing waste,in which an aerobic bioreactor is in selective fluid communication witha source of oxygen-rich liquid medium. The aerobic bioreactor isconfigured for aerobically processing waste via bacteria fixed on mediato provide processed effluent from the waste. The source of oxygen-richliquid medium is different from the aerobic bioreactor.

A feature of at least some examples of the presently disclosed subjectmatter is that the energy requirement to generate and supply oxygen tothe aerobic bioreactor is much less than would be the case if the oxygenis instead provided by an aerator or the like, for example anelectromechanical aerator.

A feature of at least some examples of the presently disclosed subjectmatter is that, by separating the aerobic treatment process of wastefrom the process of generating oxygen via photosynthetic microorganisms(for example algae), interference between the two processes can beminimized or avoided.

A feature of at least some examples of the presently disclosed subjectmatter is that, by separating the aerobic treatment process of wastefrom the process of generating oxygen via photosynthetic microorganisms(for example algae), each process can be separately and independentlyoptimized.

A feature of at least some examples of the presently disclosed subjectmatter is that, by providing bacteria fixed on media, the aerobictreatment process of waste can be easily separated from the process ofgenerating oxygen via photosynthetic microorganisms (for example algae).

A feature of at least some examples of the presently disclosed subjectmatter is that, by providing bacteria fixed on media, the efficiency ofthe aerobic treatment of waste can be enhanced as compared withproviding the bacteria without media.

A feature of at least some examples of the presently disclosed subjectmatter is that algae is produced as a byproduct of the waste treatmentprocess. Thus, the waste treatment system and method of at least someexamples of the presently disclosed subject matter is concurrently, oralternatively a system and method, respectively, for the production ofalgae, in which the algae can be harvested from the respective source ofoxygen-rich liquid medium.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the subject matter that is disclosed herein andto exemplify how it may be carried out in practice, examples will now bedescribed, by way of non-limiting example only, with reference to theaccompanying drawings, in which:

FIG. 1( a) and FIG. 1( b) are respectively a cross-sectional side viewand a plan view of a system for aerobic processing of waste according toa first example of the presently disclosed subject matter.

FIG. 2( a) and FIG. 2( b) are respectively a cross-sectional side viewand a plan view of a system for aerobic processing of waste according toa second example of the presently disclosed subject matter.

FIG. 3( a) and FIG. 3( b) are respectively a cross-sectional side viewand a plan view of a system for aerobic processing of waste according toa third example of the presently disclosed subject matter.

FIG. 4( a) and FIG. 4( b) are respectively a cross-sectional side viewand a plan view of a system for aerobic processing of waste according toa fourth example of the presently disclosed subject matter.

FIG. 5( a) and FIG. 5( b) are respectively a cross-sectional side viewand a plan view of a system for aerobic processing of waste according toa fifth example of the presently disclosed subject matter.

FIG. 6 is a cross-sectional side view of an alternative variation of theexample of FIG. 5( a) and FIG. 5( b).

FIG. 7( a), 7(b), 7(c) schematically illustrate operation of the exampleof FIG. 5( a) and FIG. 5( b) according to one example of a method of thepresently disclosed subject matter.

FIG. 8 schematically illustrates operation of the example of FIG. 5( a)and FIG. 5( b) according to one example of a method of the presentlydisclosed subject matter.

FIG. 9 schematically illustrates operation of the example of FIG. 5( a)and FIG. 5( b) according to one example of a method of the presentlydisclosed subject matter.

FIG. 10 is a cross-sectional side view of an alternative variation ofthe example of FIG. 5( a) and FIG. 5( b).

FIG. 11 is a cross-sectional side view of an alternative variation ofthe example of FIG. 5( a) and FIG. 5( b).

DETAILED DESCRIPTION

Referring to FIGS. 1( a) and 1(b), a system for aerobic processing ofwaste, in particular liquid waste, according to a first example of thepresently disclosed subject matter, generally designated 100, comprisesan aerobic bioreactor 120 and an oxygen-rich liquid medium source 150.

Such waste includes but is not limited to organic types of waste, inparticular waste water containing suspended or dissolved organic matteras well as nitrogenous components, for example animal, agricultural,industrial or human waste transported in water, and which can beaerobically treated to remove pollutants.

Aerobic bioreactor 120 comprises a vessel 122 and is configured foraerobically processing waste therein using suitable microorganisms andoxygen, the oxygen being provided via a supply of oxygen-rich liquidmedium L that is controllably recirculated between the liquid mediumsource 150 and the aerobic bioreactor 120.

Vessel 122 comprises walls 124 and defines an internal volume 126 (ofmagnitude V1), the respective aerobic processing volume. The vessel 122can have any desired or suitable shape, for example cylindrical,frusto-conical, parallelepiped, and so on, and is configured forpreventing the internal volume 126 from being irradiated byelectromagnetic radiation having wavelengths corresponding to at least apredetermined group and/or range of wavelengths. This predeterminedgroup and/or range of wavelengths consists of electromagneticwavelengths that promote growth of algae and the accompanying generationof oxygen by the algae. This predetermined group and/or range ofwavelengths is referred to herein as “light”, and typically includes thevisible light spectrum and other wavelengths associated withphotosynthesis. Thus, for example, the vessel 122 can be free-standingand the walls 124 are opaque to light. Alternatively, the vessel 122 canhave translucent or transparent (or indeed opaque) walls, but in use thevessel 122 is buried underground, or is kept in a darkened enclosure, oris covered with an opaque shield, opaque blanket, or other opaquecovering.

Such shielding of the internal volume 126 from said light can be fullshielding, i.e., fully 100% effective in preventing the internal volume126 from being irradiated by said light. Alternatively, such shieldingof the internal volume 126 from said light can be partial shielding,i.e., can be less than 100% effective, for example up to 60%, or 70% or80% or 90% or 95% or 98% or 99%, or any other percentage value inbetweenthese examples of percentages. In alternative variations of this exampleof the system, the internal volume 126 has zero shielding from saidlight.

The liquid medium source 150 comprises reservoir 152 (also referred toherein interchangeably as a tank) and is configured for providing asupply of liquid medium L that is controllably recirculated between thereservoir 152 and the aerobic bioreactor 120.

The reservoir 152 is different from and/or separate from the aerobicbioreactor 120, comprises walls 154 which define an internal volume 156(of magnitude V2), the respective reservoir algae growth volume. Theinternal volume 156 is different from and separate from the internalvolume 126 of the aerobic bioreactor 120. The reservoir 152 can have anydesired or suitable shape that is configured for allowing circulation ofthe liquid medium therein. In this example, the reservoir 152 has aclassical “raceway” configuration, comprising a generally elongatedrectangular planform 160 having generally rectilinear upstandinglongitudinal walls 164 and rounded ends 162 at the longitudinal endsthereof. A dividing wall 165 is positioned between longitudinal walls164 and laterally spaced therefrom, extending longitudinally from thecenter of planform 160 towards rounded ends 162, but leaving a spacingbetween each edge 166 of the dividing wall 165 and the respective end162. An endless, oval-shaped horizontal channel 169 is thus defined inthe reservoir 152, allowing endless flow of the liquid medium L aroundthe channel 169, driven by driver 170. In this example, the driver 170is a mechanical propulsion device, and comprises a powered paddlingsystem, including a motor 172 operatively connected to a paddle wheel174, which comprises a plurality of paddles radially radiating from anaxle that is rotatably mounted to the reservoir 152. In operation, thepaddle wheel 174 is partially submerged in the liquid medium L and isturned by the motor 172 thereby propelling the liquid medium L aroundthe channel 169 continuously in an endless loop (see arrows K, FIG.(b)).In alternative variations of this example, other arrangements can beprovided for mixing the algae in the reservoir 152, for example: amoving bridge device, a cable pulled device, and so on.

The reservoir 152 is configured for allowing the internal volume 156 tobe irradiated by said light, i.e. by electromagnetic radiation havingwavelengths at least in the aforesaid predetermined group and/or rangeof wavelengths. In this example, the reservoir 152 has an open top 153,and thus the channel 169 can have a U-shaped or V-shaped transversecross-section, for example, allowing natural sunlight to reach theliquid medium L in the channel 169 up to a particular penetration depth.In this example, the channel 169 is configured having an operationaldepth D of liquid medium L similar to the aforesaid penetration depth,but in alternative variations of this example the channel 169 can beinstead configured having operational depth D of liquid medium L greaterthan or less than the aforesaid penetration depth. The depth of thechannel 169 can be uniform across the cross-section of the channel 169,or can vary therein. For example, depth D can vary across the width ofthe channel from 30 cm at the longitudinal walls 164 to more than 1meter at the center of the channel 169, or, the entire width of thechannel 169 can be about 60 cm deep, or, the depth at the longitudinalwalls 164 can be greater than 60 cm and the center of the channel 169the depth can be greater than 2 meters deep. Optionally, the top 153 canbe covered with a translucent or transparent cover, allowing said lightto penetrate, but preventing contaminants from entering, the internalvolume 156.

In this example the reservoir 152 is configured for operation in anoutdoors environment. However, in alternative variations of this examplethe reservoir 152 can be configured for operation in an indoorsenvironment, for example a greenhouse-type structure wherein such lightmay be provided via glass panels, or for example other natural orartificial structures in which such light is provided artificially viasuitable illuminating apparatus such as electrical lamps, for example.Thus, the system 100 can optionally comprise illuminating apparatus suchas lamps, for continual use, or for periodic use, for example duringnighttime or low sunlight/overcast conditions.

System 100 comprises a recirculation circuit 180, having a reservoiroutward flow path 181 and a reservoir return flow path 183 forrecirculating the liquid medium L between the aerobic bioreactor 120 andthe reservoir 150, in particular between the internal volume 126 and theinternal volume 156. The reservoir outward flow path is provided byconduit 184, which provides fluid communication, in particular liquidcommunication, between bioreactor inlet 128 and reservoir outlet 158.The reservoir return flow path is provided by conduit 182, which thusprovides fluid communication, in particular liquid communication,between bioreactor outlet 127 and reservoir inlet 157.

In this example, the recirculation circuit 180 further comprises a pump185 for driving the aforesaid recirculation of the liquid medium Lbetween the aerobic bioreactor 120 and the reservoir 150. For example,such a pump 185 can be a submersible pump, for example: XFP-8c-201gprovided by ABS of Malmo, Sweden; or pump D-3000 provided by Flygt, ofStockholm, Sweden; or a dry mounted external pump, for example FRprovided by ABS of Malmo, Sweden; or pump N-3000 provided by Flygt, ofStockholm, Sweden; or pump DWK, provided by Grundfoss of Bjerringbo,Denmark.

Optionally, part of the pumping may be carried out via gravity, and thuspump 185 can optionally comprise a gravity pump system. For example,flow of liquid medium L along the reservoir outward flow path 181 is viagravity, while a powered pump forces the flow of liquid medium L throughthe reservoir return flow path 183, or, flow of liquid medium L alongthe reservoir return flow path 183 is via gravity, while a powered pumpforces the flow of liquid medium L through the reservoir outward flowpath 181.

The liquid medium source 150, in particular the reservoir 152, isconfigured for generating and providing oxygen to liquid medium L, sothat the oxygen-rich liquid medium L can be provided to the aerobicbioreactor 120 (via conduit 184). The generation of oxygen isaccomplished by the photosynthetic action of photosyntheticmicroorganisms, in particular photosynthetic eukaryotic or prokaryoticmicroorganisms for example algae, (that are carried in the liquid mediumL), when illuminated by said light and provided with appropriatenutrients. In this example, in which the reservoir 152 has an open top153, carbon in the form of CO₂ is provided from the atmosphere bynatural diffusion via the surface of the liquid medium L, and nutrientsrequired for the biological process are provided from the incoming wastewater.

Such photosynthetic microorganisms can include any suitablephotosynthetic eukaryotic microorganisms or photosynthetic prokaryoticmicroorganisms. For example, suitable photosynthetic eukaryoticmicroorganisms include algae, for example any one of the following:Chlorella, Scenedesmus, Spirulina, diatoms, and so on. In addition,suitable photosynthetic prokaryotic microorganisms include cyanobacteria(also known as “blue-green algae”) that can also serve as aphotosynthetic source of oxygen.

Thus, while the disclosure herein refers to algae per se, it is to benoted that the disclosure applies, mutatis mutandis, to any otherphotosynthetic eukaryotic or prokaryotic microorganisms, for example aslisted above.

The algae are thoroughly mixed within liquid medium L and arecontinually or cyclically exposed to the illuminating light by themotion around the channel 169 provided by driver 170, and the oxygenproduced by the algae is dissolved in the liquid medium L.

The system 100 further comprises a waste inlet 132 (optionally includinga valve, not shown) at the aerobic bioreactor 120 for receiving wasteinto the internal volume 126 and that is to be treated aerobically bythe system 100. The system also comprises a treated effluent outlet 134with valve 131, for dispensing treated effluent that results fromaerobically treating the waste that is supplied to the aerobicbioreactor 120. While in this example, the effluent outlet 134 isprovided at the reservoir 152, in alternative variations of this examplethe effluent outlet 134 can instead be provided at the aerobicbioreactor 120.

In the illustrated example of FIGS. 1( a) and 1(b), the aerobicbioreactor 120 and oxygen-rich liquid medium source 150 are shown inside-by-side configuration in system 100. However, in alternativevariations of this example the aerobic bioreactor 120 and oxygen-richliquid medium source 150 can have any suitable relative spatialrelationship: for example, the aerobic bioreactor 120 can be positionedbeneath the oxygen-rich liquid medium source 150.

As already mentioned, the aerobic bioreactor 120 is configured foraerobically processing waste using suitable microorganisms and oxygenprovided by oxygen-rich liquid medium L. Such microorganisms can includefor example any one of the following: saprophytic bacteria,heterotrophic bacteria, autotrophic bacteria, protozoa, metazoa,rotifers, and others.

In particular, the microorganisms are fixed on media 190. Such media 190comprise biofilm carrier elements, in the form of substrates, inparticular solid inert substrates, having a relatively large surfacearea to volume ratio R. Such substrates can include, for example, anyone of polyethylene or other plastics, and the respective surface areato volume ratio R can be, for example, between about 500 m²/m³ and about1300 m²/m³, for example about 650 m²/m³. Alternatively, substrates caninclude, for example, any one of metallic materials, fibers, cloths,mineral materials (such as for example carbon, volcanic tuff, gravel),and so on, at least some of which can have respective surface area tovolume ratios R much higher than 1300 m²/m³.

These substrates thus enable large amounts of microorganisms to be fixedon the surface of the substrates as a biofilm, provide a stable matrixfor the microorganisms, support aerobic, facultative or anaerobicconsortia of microorganisms, and allow optimal interaction between themicroorganisms and the waste, which the microorganisms digestaerobically utilizing the dissolved oxygen provided by the liquid mediumL.

In this example, the media 190 are mobile, i.e. free-floating media,configured for moving within the liquid mixture Q in the internal volume126, the liquid mixture Q including liquid medium L, waste W, andprocessed effluent E in varying proportions during operation of thesystem 100.

In this example, the free-floating media 190 are prevented from leavingthe aerobic bioreactor 120 and from being transported via recirculationcircuit 180 to the reservoir 152, at least during operation of thesystem 100. For this purpose the aerobic bioreactor 120 comprisessuitable mechanical filters, screens or other selective barriers (notshown) at the bioreactor outlet 127, and optionally also at thebioreactor inlet 128, that prevent passage of the media 190therethrough, while allowing flow of the liquid medium L therethrough.

Examples of such media 190 include one or more of the following: AqwiseBiomass Carriers (ABC 5), provided by Aqwise, Israel; biocarriers K1 orK3, provided by Veolia, France, ActivCell provided by Degremont, France.

In alternative variations of this example, media 190 is, or alsoadditionally comprises, fixed media. Such fixed media are affixed insitu with respect to the location thereof within the internal volume126, and thus are prevented from leaving the aerobic bioreactor 120 andfrom being transported via recirculation circuit 180 to the reservoir152, even in the absence of mechanical filters or screens at thebioreactor outlet 127 and/or at the bioreactor inlet 128. Such fixedmedia includes types of media in which the substrate is fixed on one ormore sides thereof to the structure of the vessel 122. For example, suchfixed media can be in the form of a plastic matrix attached to the flooror sides of the vessel 122, and/or ropes or fibers hanging within theliquid in the vessel 122 and attached either to the walls or otherstructure of the vessel 122 or attached to a rigid frame located withinthe vessel 122. Examples of such fixed media can include one or more ofthe following: AccuFAS PVC carrier material, provided by BrentwoodCorporation, USA; Bioclere media material provided by Aquapoint, USA;Ringlace biomaedia provided by Ringlace Products, USA.

Alternatively, the fixed media is not necessarily actually attached tothe inside of the aerobic bioreactor, but rather comprises a quantity ofmedia which by virtue of its own weight (e.g., a pile of gravel media)remains in a single location in the aerobic bioreactor.

In this example, the aerobic bioreactor 120 further comprises a mixingdevice 149, configured for mixing the media 190 within the liquidmixture Q, while minimizing or preventing damage to the media 190. Inthis example, the mixing device comprises a powered stirrer, for examplefor example submersible mixers POPR-I provided by Landia, of Sweden, ormixer RW-400 provided by ABS of Sweden, or mixer 4850 top entry mixerprovided by Flygt, of Sweden.

Optionally, the system 100 can further comprise an auxiliary aerationsystem, (not shown) configured for selectively providing gaseous oxygenor air to the aerobic bioreactor 120, for example comprising a pump orsource of compressed air having an outlet in selective communicationwith the internal volume 126. Such an auxiliary aeration system can beused, for example, during operation of system 100 at nighttime or in lowsunlight/overcast conditions, or whenever oxygen production by thesource 150 is lower than required, or indeed whenever desired.

Optionally, the system 100 can further comprise an auxiliary CO₂ system,(not shown) configured for selectively providing gaseous carbon dioxideor carbon-dioxide rich air to the liquid source 150, for examplecomprising a pump or source of compressed gaseous carbon dioxide orcarbon-dioxide rich air having an outlet in selective communication withthe internal volume 156. Such an auxiliary CO₂ system can be used, forexample, whenever additional CO₂ is required for oxygen production bythe source 150, or indeed whenever desired.

Operation of system 100 in a continuous flow mode (CFM) can be asfollows.

Waste W, mainly in liquid form, is conveyed to the aerobic bioreactor120 at a flow rate T1 via waste inlet 132, the waste W first havingfirst been subjected to preprocessing, including a screening anddegritting process to remove solids, with or without a preliminaryanaerobic treatment process. Concurrently, there is provided arecirculating flow of liquid medium L between the reservoir 152 and theaerobic bioreactor 120 via recirculation circuit 180, at a flow rate T2.The liquid medium L also carries algae to and from the reservoir 152 viarecirculation circuit 180. The liquid medium L in reservoir 152 is beingcontinuously provided with oxygen generated by the algae therein as theliquid medium L is exposed to said light and provided with nutrients,and this oxygen generation process is enhanced by forcing the liquidmedium L to flow along channel 169 by the action of the driver 170.Thus, the liquid medium L delivered to the aerobic bioreactor 120 viaconduit 184 is oxygen-rich.

The microorganisms fixed in media 190 treat the waste aerobically, usingoxygen dissolved in the liquid medium L delivered from the reservoir152, thereby converting the waste W into processed effluent E. Theeffluent E leaves the aerobic bioreactor 120 via conduit 182 under theaction of pump 185, and flows into the reservoir 152, to be dispensedvia dispensing outlet 134 at flow rate T3.

In practice, a mixture M1 of the processed effluent E, (partiallyde-oxygenized) liquid medium L, and possibly waste W, in varyingproportions, leaves the aerobic bioreactor 120 via conduit 182.Similarly, a mixture M2 of the processed effluent E, (oxygen-rich)liquid medium L, and possibly waste W, in varying proportions,circulates back and enters the aerobic bioreactor 120 via conduit 184.Similarly, a mixture M3 of the processed effluent E, liquid medium L,and possibly waste W, in varying proportions, is dispensed via thedispensing outlet 134. However, the system 100 is also set up such thatin steady-state operating conditions, mixture M1 has a high proportionof effluent E relative to waste W, mixture M2 has a high proportion ofliquid medium L relative to waste W or effluent E, and mixture M3 has ahigh proportion of effluent E relative to waste W.

This effect can be achieved as follows, for example. In steady stateconditions, the waste input flow rate T1 is about the same as effluentoutput flow rate T3, and the liquid medium L flow rate recirculatingbetween the reservoir 152 and the aerobic bioreactor 120 T2 is greaterthan flow rate T1 or T3; for example T2 can be from 2 to 10 timesgreater than T1 or T3. At the same time, the flow rates T1, T2, T3 aresuch (when compared with the sizes V1 and V2, respectively, of internalvolumes 126 and 156) so as to allow the waste W sufficient residencetime (also referred to interchangeably herein as retention time) in theaerobic bioreactor 120 to become processed by the microorganisms in themedia 190, and so as to allow the algae sufficient residence time in thereservoir 152 to generate the required levels of oxygen therein.

For example, the volume ratio V2/V1 of the respective internal volumes126 and 156 can be between about 1 to about 10, or greater; additionallyor alternatively, the retention time ratio V1/T1 or V1/T3 can be betweenabout 5 hours to about 20 hours or greater, for example 8 hours;additionally or alternatively, the retention time ratio V1/T2 can bebetween about 1.0 hours to about 20 hours or greater, for example 2.7hours; additionally or alternatively, the retention time ratio V2/T1 orV2/T3 can be between about 10 hours to about 40 hours or greater, forexample 24 hours; additionally or alternatively, the retention timeratio V2/T2 can be between about 3 hours to about 20 hours or greater,for example 8 hours.

For example, the internal volume 126 can be configured for providing aretention time for the waste therein of between 2 to 12 hours, for agiven flow rate T1 of waste W into the aerobic bioreactor 120. Forexample, the internal volume 156 can be configured for providing aretention time for the liquid medium L including algae therein ofbetween 8 to 72 hours, for a given flow rate T2 of liquid medium L into(and out of) the aerobic bioreactor 120 via recirculation circuit 180.

For example, to provide this effect, the internal volume 126 can beabout 400 liters, waste flow rate T1 into the aerobic bioreactor 120 canbe about 50 liters/hour, the internal volume 156 can be about 1200liters, the liquid medium flow rate T2 into the aerobic bioreactor 120can be about 150 liters/hour, and the processed effluent flow rate T3out of the system 100 can be about 50 liters/hour. In another examplethis effect can be provided with the following parameters: the internalvolume 126 can be about 400 cubic meters, waste flow rate T1 into theaerobic bioreactor 120 can be about 50 m³/hour, the internal volume 156can be about 1200 cubic meters, the liquid medium flow rate T2 into theaerobic bioreactor 120 can be about 350 m³/hour, and the processedeffluent flow rate T3 out of the system 100 can be about 50 m³/hour. Ofcourse, other examples of the magnitude of the flow rates T1, T2, T3 andof the magnitudes V1, V2, respectively of the internal volume 126 andthe internal volume 156, can be chosen to provide the aforementionedeffect.

Thus, in operation of the system 100, the microorganisms aerobicallytreat the waste W in internal volume 126 and in the absence of saidlight, i.e., in darkened conditions, which are optimal for themicroorganisms, while being provided with ample oxygen dissolved in theliquid medium L. In the darkened conditions provided by the aerobicbioreactor 120, the algae that is recirculating through the aerobicbioreactor 120 are thus under conditions that do not promote furthergrowth, and thus minimize interference with the aerobic processing ofthe waste by the microorganisms. Furthermore, the provision of themicroorganism as a biofilm fixed on media 190, in which themicroorganism are exposed to the waste W and oxygen-rich liquid medium Lover a large surface area relative to the volume occupied by the media190, enables the waste W to be processed faster and more efficientlythan would be the case if the microorganism were instead provided as asludge moving throughout the system, for example.

On the other hand, the conditions for generating oxygen by the algae insource 150 are also concurrently optimal, the algae receiving said lightand nutrients in the reservoir 152, and kept in motion around thechannel 169 by the action of the driver 170. Further, these conditionsare further optimized by the relative absence of the microorganisms inthe reservoir 152, since the microorganisms, being fixed on the media190, are prevented from being transported to the reservoir 152 from theaerobic bioreactor 120.

Thus, the aerobic treatment process of waste is independent andseparated from the process of generating oxygen via algae, avoiding orminimizing interference between the two processes, and each process canbe separately and independently optimized.

For a given requirement of throughput of waste through the aerobicbioreactor 120, the reservoir 152 can be sized accordingly whereby toprovide the necessary oxygen demand for the bioreactor 120.

The energy requirements for operating the system 100 are thus relativelymodest, including the power required for operating the pumps 185,149,and the driver 170.

The system 100 can optionally further comprise post-processing systemsfor post-processing the effluent E. For example, downstream of effluentoutlet 134 can be provided further filters and purifiers to furtherpurify the effluent E. For example, a plurality of systems 100 can beconnected in series, with the first one receiving waste W, and havingits effluent outlet 134 connected to the waste inlet 132 of the nextsystem 100 (thus the effluent from the first system is considered as the“waste” being supplied to the next system), which is similarly connectedto the next system, and so on, the last system 100 then dispensing themany-times processed effluent E.

It is to be noted that the aerobic processing of the waste in theaerobic bioreactor 120 generates CO₂ as a byproduct, and this CO₂ can berouted to the reservoir 152 (via suitable piping or the existing liquidflows, for example) to provide additional carbon to the algae therein.Alternatively, the biogas itself, which is rich in CO₂, can be used toenrich the algae with a carbon source by injecting it through the liquidmedium L.

It is also to be noted that in the aforementioned preprocessing in theform of said anaerobic treatment process, biogas can be generated. Thisbiogas can be sold off, or can be utilized for power generation, forexample for powering the system 100, and the CO₂ produced as a byproductof said power generation can also be routed to the reservoir 152 viasuitable piping for example to provide additional nutrients to the algaetherein.

Alternatively, system 100 can be operated in batch mode (BM), forexample as follows. Waste W (after the aforesaid preprocessing) isprovided to the aerobic bioreactor 120 until it reaches a particularlevel. The waste input is turned off at waste inlet 128, and theeffluent outlet 134 is also closed. The reservoir is operated as in CFMabove, mutatis mutandis, to provide a flow rate of liquid medium Lthrough aerobic bioreactor 120, providing oxygen to the aerobicbioreactor 120, and allowing the aerobic bioreactor 120 and thereservoir to each operate under its own optimal conditions, but withoutcontinuous addition of waste W or dispensing of effluent E. Themicroorganisms that are fixed on media 190 aerobically process the wastein a similar to that of the CFM disclosed above, mutatis mutandis,typically by digesting or decomposing the waste, and when all or most ofthe waste is processed, the processed effluent can be drained from theaerobic bioreactor 120 or via the reservoir 152, through thecorrespondingly-located effluent outlet 131, though in practice sucheffluent is mixed in with liquid medium L.

Referring to FIGS. 2( a) and 2(b), a second example of the system,generally designated 200, comprises the elements and features of system100 of the first example and operates in a similar manner thereto,mutatis mutandis, but with some differences, as will become clearerherein. Thus, system 200 comprises aerobic bioreactor 220 and anoxygen-rich liquid medium source 250, similar to aerobic bioreactor 120and oxygen-rich liquid medium source 150, mutatis mutandis, but withsome differences.

Liquid medium source 250 comprises reservoir 252 (similar to reservoir152, mutatis mutandis) and is configured for providing a supply ofliquid medium L that is controllably recirculated between the reservoir252 and the aerobic bioreactor 220. Liquid medium source 250 isdifferent from and separate from the aerobic bioreactor 220.

The reservoir 252 similarly comprises walls 254 and defines an internalvolume 256, different from and separate from the internal volume 226 ofthe aerobic bioreactor 220. While in alternative variations of thisexample the reservoir 252 can have any suitable shape, in this examplethe reservoir has a classical “raceway” configuration, similar to thereservoir 152 of the first example, mutatis mutandis, comprising agenerally elongated rectangular planform 260, including generallyrectilinear upstanding longitudinal walls 264, rounded ends 262,dividing wall 265, endless oval-shaped horizontal channel 269 allowingendless flow of the liquid medium L around the channel 269, driven bydriver 270, respectively similar in form and function to: planform 160,generally rectilinear upstanding longitudinal walls 164, rounded ends162, dividing wall 165, endless oval-shaped horizontal channel 169 anddriver 170, mutatis mutandis. As with the first example, mutatismutandis, the reservoir 252 is configured for allowing the internalvolume 256 to be irradiated by said light, i.e. by electromagneticradiation at least of the aforesaid predetermined group and/or range ofwavelengths, and in the second example the reservoir 252 also has anopen top 253, which optionally, can be covered with a translucent ortransparent cover, allowing light to penetrate, but preventingcontaminants from entering, the internal volume 256.

Aerobic bioreactor 220 comprises a vessel 222 and is configured foraerobically processing waste therein using suitable microorganisms andoxygen, in a similar manner to aerobic reactor 120 and vessel 122,mutatis mutandis, but with some differences, as will become clearerherein. This oxygen is provided via a supply of oxygen-rich liquidmedium L that is controllably recirculated between the liquid mediumsource 250 and the aerobic bioreactor 220.

Vessel 222 comprises walls 224 and defines an internal volume 226.Vessel 222 can have any desired or suitable shape, and is configured forpreventing the internal volume 226 from being irradiated by said light,and comprises microorganisms fixed in media 190, in a similar manner asdisclosed herein for vessel 122 and media 190 of the first example,mutatis mutandis.

In the second example, vessel 222 located beneath the reservoir 252 andboth components can optionally be constructed as an integral structure,or as two separate structures joined together.

In the second example, the respective recirculation circuit 280 is alsoconfigured for recirculating the liquid medium L between the aerobicbioreactor 220 and the reservoir 250, in particular between the internalvolume 226 and the internal volume 256. The recirculation circuit 280also has a reservoir outward flow path and a reservoir return flow path,but differs from the recirculation circuit 180 of the first example asfollows. The reservoir outward flow path to the aerobic bioreactor 220is via bioreactor inlet 228 which also acts as the reservoir outlet 258,while the reservoir return flow path is via conduit 284 that connectsbioreactor outlet 227 with reservoir inlet 257.

The bioreactor inlet 228/reservoir outlet 258 is located at an upperportion of the vessel 222, and also located in the channel 269 andsubmerged within the liquid medium L therein at least during operationof the system 200. The recirculation circuit 280 further includes avalve arrangement 281 for selectively controlling what proportion of theflow of liquid medium L around the circuit 269 is diverted to theaerobic bioreactor 220. In the illustrated example, the valvearrangement 281 is in the form of a movable weir, pivotably mounted atthe bioreactor inlet 228/reservoir outlet 258 and operates to pivotabout the respective pivot axis to change the effective inlet area ofthe bioreactor inlet 228/reservoir outlet 258.

The bioreactor outlet 227 is located at a lower portion of the vessel222, while reservoir inlet 257 opens into the channel 269 and submergedwithin the liquid medium L therein at least during operation of thesystem 200.

In this example, the free-floating media 190 are also prevented fromleaving the aerobic bioreactor 220 and from being transported viarecirculation circuit 280 to the reservoir 252, at least duringoperation of the system 200. For this purpose the aerobic bioreactor 220comprises suitable mechanical filters or screens 289 at the bioreactoroutlet 227, and optionally also at the bioreactor inlet 228/reservoiroutlet 258 (not shown), that prevent passage of the media 190therethrough, while allowing flow of the liquid medium L therethrough.Alternatively, free-floating media 190 can be replaced with fixed mediaas in the first example of system 100, mutatis mutandis and no suchfilters or screens are necessary and can be omitted.

In this example, the recirculation circuit 280 further comprises a pump285 for driving the aforesaid recirculation of the liquid medium Lbetween the aerobic bioreactor 220 and the reservoir 252. In theillustrated example, such a pump 285 is in the form of an airlift pump,powered by a blower, and located at the bottom end of the conduit 284.Such an airlift pump may comprise, for example, one or more of thefollowing: Robox provided by Robuschi of Italy, or Delta Blower providedby Aerzen, of the USA; or Roots Blowers provided by GE of the USA.Optionally, the air introduced into the conduit 284 by the airlift pumpcan be enriched in CO₂, or can be replaced with CO₂, which can enhancegrowth of the algae in the reservoir 252 and generation of oxygen. Inalternative variations of this example, pump 285 can have any othersuitable form, for example similar to pump 185 as disclosed above forthe first example, mutatis mutandis.

In this example, the aerobic bioreactor 220 can optionally furthercomprise a mixing device (not shown), for example similar to the mixingdevice 149 of the first example of system 100, mutatis mutandis, and isconfigured for mixing the media 190 within the liquid mixture Q in thevessel 222, while minimizing or preventing damage to the media 190.

System 200 also comprises a waste inlet 232 and a processed effluentoutlet 234, which in this example are provided in the reservoir 252 butin other alternative variations of this example can be provided directlyto reservoir 220 instead.

Operation of the system 200 in CFM or in BM is as disclosed above forthe first example of system 100 optionally including preprocessingand/or post-processing, mutatis mutandis, with the main difference beingthat the respective flow rate T2 of recirculating flow of liquid mediumL between the reservoir 252 and the aerobic bioreactor 220 viarecirculation circuit 280, is controlled by the flow rate of the liquidmedium L around the channel 269 coupled with the effective flow area atthe bioreactor inlet 228/reservoir outlet 258, which is controlled bythe valve arrangement 281 and by the flow of air from pump 285.

Referring to FIGS. 3( a) and 3(b), a third example of the system,generally designated 300, comprises the elements and features of system100 of the first example (or similarly of system 200 of the secondexample) and operates in a similar manner thereto, mutatis mutandis, butwith some differences, as will become clearer herein. Thus, system 300comprises aerobic bioreactor 320 and an oxygen-rich liquid medium source350, similar to aerobic bioreactor 120 and oxygen-rich liquid mediumsource 150, mutatis mutandis, but with some differences.

Liquid medium source 350 comprises reservoir 352, which similarly toreservoir 152, mutatis mutandis, is configured for providing a supply ofliquid medium L that is controllably recirculated between the reservoir352 and the aerobic bioreactor 320, and is different from and separatefrom the aerobic bioreactor 320.

The reservoir 352 similarly comprises walls 354 and defines an internalvolume 356, different from and separate from the internal volume 326 ofthe aerobic bioreactor 320. While in alternative variations of thisexample the reservoir 352 can have any suitable shape, in this examplethe reservoir has a modified “raceway” configuration, similar to thereservoir 152 of the first example, mutatis mutandis, but in which thedividing wall 165 is replaced with a cylindrical wall 365. Thus,reservoir 352 comprises a generally annular planform 360, includinggenerally cylindrical upstanding outer wall 364, and the inner saidcylindrical wall 365, defining an endless annular-shaped horizontalchannel 369 allowing endless flow of the liquid medium L around thechannel 369, driven by driver 370, the channel 369 and driver 370 beingrespectively similar in form and/or function to endless oval-shapedhorizontal channel 169 and driver 170, mutatis mutandis. As with thefirst example, mutatis mutandis, the reservoir 352 is configured forallowing the internal volume 356 to be irradiated by said light, i.e. byelectromagnetic radiation at least of the aforesaid predetermined groupand/or range of wavelengths, and in the third example the reservoir 352also has an open top 353, which optionally, can be covered with atranslucent or transparent cover, allowing light to penetrate, butpreventing contaminants from entering, the internal volume 356.

Aerobic bioreactor 320 comprises a vessel 322 and is configured foraerobically processing waste therein using suitable microorganisms andoxygen, in a similar manner to aerobic reactor 120 and vessel 122,mutatis mutandis, but with some differences, as will become clearerherein. This oxygen is provided via a supply of oxygen-rich liquidmedium L that is controllably recirculated between the liquid mediumsource 350 and the aerobic bioreactor 320.

Vessel 322 comprises walls 324 and defines an internal volume 326.Vessel 322 can have any desired or suitable shape, is configured forpreventing the internal volume 326 from being irradiated by said light,and comprises microorganisms fixed in media 190, in a similar manner asdisclosed herein for vessel 122 and media 190 of the first example,mutatis mutandis.

In the third example, vessel 322 located within the inner wall 365 andextends to a depth below that of the reservoir 352, and both componentscan optionally be constructed as an integral structure, or as twoseparate structures joined together. In particular, the outercylindrical walls 324 of vessel 322 can act as inner cylindrical wall365. Alternatively, in alternative variations of this example, thevessel 322 can be spaced from inner cylindrical wall 365 by a gap. Forexample, the vessel 322 can have a depth of between about 1 m and about10 m.

In the third example, the respective recirculation circuit 380 is alsoconfigured for recirculating the liquid medium L between the aerobicbioreactor 320 and the reservoir 350, in particular between the internalvolume 326 and the internal volume 356. The recirculation circuit 380also has a reservoir outward flow path and a reservoir return flow path,but differs from the recirculation circuit 180 of the first example asfollows.

The reservoir outward flow path to the aerobic bioreactor 320 is viabioreactor inlet 328 which also acts as the reservoir outlet 358, whilethe reservoir return flow path is via conduit 384 that connectsbioreactor outlet 327 with reservoir inlet 357.

The bioreactor inlet 328/reservoir outlet 358 is located at an upperportion of the vessel 322, and also located in the channel 369 andsubmerged within the liquid medium L therein at least during operationof the system 300. The bioreactor inlet 328/reservoir outlet 358 opensinto a conduit 383 within vessel 322, having an upper opening 388 and alower opening 387 within internal volume 326.

The bioreactor outlet 327 is located at an upper portion of the vessel322, well above the level of liquid medium L in the channel 369, and thereservoir inlet 357 is also located above the reservoir 352, and liquidflows along the reservoir return flow path from the aerobic bioreactor320 to the reservoir 352 when the level of liquid in the aerobicbioreactor 320 tries to exceed the level of the bioreactor outlet 327.In alternative variations of this example, the bioreactor outlet 327and/or the reservoir inlet 357 can be located elsewhere in the system300, for example the reservoir inlet 357 can be located in the channel369 and submerged within the liquid medium L therein at least duringoperation of the system 300.

In this example, the recirculation circuit 380 further comprises a pump385 for driving the aforesaid recirculation of the liquid medium Lbetween the aerobic bioreactor 320 and the reservoir 352. In theillustrated example, such a pump 385 is in the form of an airlift pump,powered by a compressor, and located at the bottom end of the conduit383, near lower opening 387. Such an airlift pump may comprise, forexample, any one of; Robox provided by Robuschi of Italy; or DeltaBlower provided by Aerzen, of the USA; or Roots Blowers, provided by GEof the USA. As a gas such as air is introduced into conduit 383, anupward flow is induced in conduit 383, drawing in fluid from internalvolume 326, which in turn acts as a venture at the bioreactor inlet328/reservoir outlet 358 to draw in liquid medium from the channel 369.Thus, pump 385 is located close to the bioreactor inlet 328/reservoiroutlet 358.

Optionally, the air introduced into the conduit 383 by the airlift pumpcan be enriched in CO₂, or can be replaced with CO₂, which can enhancegrowth of the algae in the reservoir 352 and generation of oxygen. Inalternative variations of this example, pump 285 can have any othersuitable form, for example similar to pump 185 as disclosed above forthe first example, mutatis mutandis. In operation of the system 300, theCO₂ is entrained and dissolved in the liquid in the aerobic reactor 320,and subsequently flows out the aerobic reactor 320 and into thereservoir 352 together with this liquid. In alternative variations ofthis example, the pump 385 can be located at bioreactor outlet 327instead of close to the bioreactor inlet 328/reservoir outlet 358,mutatis mutandis, thereby increasing efficiency of the CO₂ usage; insuch an example, the hydraulic relationship between the aerobic reactor320 and the reservoir 352 can be changed, with the level of liquid ofthe aerobic reactor 320 being lower than the level of liquid in thereservoir 352 (in contrast, in the example illustrated in FIG. 3( a),the level of liquid of the aerobic reactor 320 is higher than the levelof liquid in the reservoir 352).

In this example, the free-floating media 190 are also prevented fromleaving the aerobic bioreactor 320 and from being transported viarecirculation circuit 280 to the reservoir 352, at least duringoperation of the system 300. For this purpose the aerobic bioreactor 320comprises suitable mechanical filters or screens (not shown) at thebioreactor outlet 327, and optionally also at the bioreactor inlet328/reservoir outlet 358 (not shown), that prevent passage of the media190 therethrough, while allowing flow of the liquid medium Ltherethrough. Alternatively, free-floating media 190 can be replacedwith fixed media as in the first example of system 100, mutatis mutandisand no such filters or screens are necessary and can be omitted.

In this example, the aerobic bioreactor 320 further comprises a mixingdevice 349, similar to the mixing device 149 of the first example ofsystem 100, and is configured for mixing the media 190 within the liquidmixture Q in the vessel 322, while minimizing or preventing damage tothe media 190. In this example, the mixing device comprises a poweredstirrer, which can be for example any one of the following: submersiblemixers POPR-I provided by Landia, of Sweden; or mixer RW-400 provided byABS of Sweden; or mixer 4850 top entry mixer provided by Flygt, ofSweden.

System 300 also comprises a waste inlet 332, provided into the aerobicbioreactor 320, and a processed effluent outlet 334, which in thisexample is provided in the reservoir 352.

Operation of the system 300 in CFM or in BM is as disclosed above forthe first example of system 100 or second example of system 200optionally including preprocessing and/or post-processing, mutatismutandis, with the main difference being that the respective flow rateT2 of recirculating flow of liquid medium L between the reservoir 352and the aerobic bioreactor 320 via recirculation circuit 380, iscontrolled by the flow rate of the liquid medium L around the channel369 coupled with the pumping action of pump 385, and providing a morecompact layout.

Referring to FIGS. 4( a) and 4(b), a fourth example of the system,generally designated 400A, comprises two self-contained systems 400operating in parallel, though in other alternative variations of thisexample the system 400A can comprise only one system 400. In yet otheralternative variations of this example the system 400A can comprise morethan two systems 400, operating in parallel or in series, or two systems400 operating in series, or any other combination or permutation of twoor more two systems 400, mutatis mutandis.

Each system 400 comprises the elements and features of system 100 of thefirst example, and in particular of the system 200 of the second exampleand operates in a similar manner thereto, mutatis mutandis, but withsome differences, as will become clearer herein. Each system 400comprises an aerobic bioreactor 420 and an oxygen-rich liquid mediumsource 450, similar to aerobic bioreactor 120 and oxygen-rich liquidmedium source 150, mutatis mutandis, but with some differences.

Liquid medium source 450 comprises reservoir 452 (similar to reservoir152, mutatis mutandis, is configured for providing a supply of liquidmedium L that is controllably recirculated between the reservoir 452 andthe aerobic bioreactor 420, and is different from and separate from theaerobic bioreactor 220.

The reservoir 452 similarly comprises walls 454 and defines an internalvolume 456, different from and separate from the internal volume 426 ofthe aerobic bioreactor 420. While in alternative variations of thisexample the reservoir 252 can have any suitable shape, in this examplethe reservoir also has a classical “raceway” configuration, similar tothe reservoir 152 of the first example, mutatis mutandis, comprising agenerally elongated rectangular planform 460, including generallyrectilinear upstanding longitudinal walls 464, rounded ends 462,dividing wall 465, endless oval-shaped horizontal channel 469 allowingendless flow of the liquid medium L around the channel 469, driven bydriver 470, respectively similar in form and function to: planform 160,generally rectilinear upstanding longitudinal walls 164, rounded ends162, dividing wall 165, endless oval-shaped horizontal channel 169 anddriver 170, mutatis mutandis. As with the first example, mutatismutandis, the reservoir 452 is configured for allowing the internalvolume 456 to be irradiated by said light, i.e. by electromagneticradiation at least of the aforesaid predetermined group and/or range ofwavelengths, and in the second example the reservoir 452 also has anopen top 453, which optionally, can be covered with a translucent ortransparent cover, allowing light to penetrate, but preventingcontaminants from entering, the internal volume 456.

Aerobic bioreactor 420 comprises a vessel 422 and is configured foraerobically processing waste therein using suitable microorganisms andoxygen, in a similar manner to aerobic reactor 120 and vessel 122,mutatis mutandis, but with some differences, as will become clearerherein. This oxygen is provided via a supply of oxygen-rich liquidmedium L that is controllably recirculated between the liquid mediumsource 450 and the aerobic bioreactor 420.

Vessel 422 comprises walls 424 and defines an internal volume 426.Vessel 422 can have any desired or suitable shape, and is configured forpreventing the internal volume 426 from being irradiated by said light,and comprises microorganisms fixed in media 190, in a similar manner asdisclosed herein for vessel 122 and media 190 of the first example,mutatis mutandis. Optionally, walls 424 can in fact be parts of thewalls 454 of the reservoir 452.

In the fourth example, vessel 422 is located within the reservoir 452,in particular vessel 422 is accommodated in the channel 469, and bothcomponents—vessel 422 and the reservoir 452—can optionally beconstructed as an integral structure, or as two separate structuresjoined together.

In the fourth example, the respective recirculation circuit 480 isprovided directly by the circulating flow in the channel 469, whichdirectly recirculates the liquid medium L between the aerobic bioreactor420 and the channel 469 in reservoir 452, in particular between theinternal volume 426 and the internal volume 456. The recirculationcircuit 480 also has a reservoir outward flow path and a reservoirreturn flow path, but differs from the recirculation circuit 180 of thefirst example as follows. The reservoir outward flow path to the aerobicbioreactor 420 is via bioreactor inlet 428 which is in opencommunication with the reservoir outlet 458 at the channel 469, whilethe reservoir return flow path is via bioreactor outlet 427 which is inopen communication with the reservoir inlet 457 at the channel 469.Thus, as liquid medium L is forced around the channel 469 using driver470, it is also passed through the aerobic bioreactor 420, and noadditional pump is required for the recirculation circuit 480.

In this example, the free-floating media 190 are also prevented fromleaving the aerobic bioreactor 420 and from being transported viarecirculation circuit 480 to the reservoir 452, at least duringoperation of the system 400. For this purpose the aerobic bioreactor 420comprises suitable mechanical filters or screens 489 at the bioreactoroutlet 427 and also at the bioreactor inlet 428, that prevent passage ofthe media 190 therethrough, while allowing flow of the liquid medium Ltherethrough. Alternatively, free-floating media 190 can be replacedwith fixed media as in the first example of system 100, mutatis mutandisand no such filters or screens are necessary and can be omitted.

System 400 also comprises a waste inlet 432 opening directly into theaerobic bioreactor 420, and controllable via valve 435, and a processedeffluent outlet 434, which in this example is provided in the reservoir452, and is controllable via valve 431. For example, valves 435 and 431can be motorized valves, the operation of which is controlled manuallyand/or via an automated controller, for example electronic control,computer control, hydraulic control, and so on.

Operation of the system 400 in BM is as disclosed above for the firstexample of system 100 optionally including preprocessing and/orpost-processing, mutatis mutandis, with the main difference being thatthe respective flow rate T2 of recirculating flow of liquid medium Lbetween the reservoir 452 and the aerobic bioreactor 420, is controlledby the flow rate of the liquid medium L around the channel 469.

In yet other alternative variations of the above first, second, third,or fourth examples, and alternative variations thereof, the algae isreplaced with any other photosynthetic eukaryotic microorganisms orphotosynthetic prokaryotic microorganisms, mutatis mutandis, for exampleas listed above.

Referring to FIGS. 5( a) and 5(b), a system for aerobic processing ofwaste, in particular liquid waste, according to a fifth example of thepresently disclosed subject matter, generally designated 500, comprisesan aerobic bioreactor 520 and an oxygen-rich liquid medium source 550,similar to aerobic bioreactor 120 and oxygen-rich liquid medium source150, mutatis mutandis, but with some differences as will become clearerbelow.

Aerobic bioreactor 520 comprises a vessel 522 and is configured foraerobically processing waste therein using suitable microorganisms andoxygen, the oxygen being provided via a supply of oxygen-rich liquidmedium L that is selectively and controllably recirculated between theliquid medium source 550 and the aerobic bioreactor 520.

Vessel 522 comprises lateral walls 524 and bottom base 523, and definesan internal volume 526 (for example, of magnitude V1), the respectiveaerobic processing volume. While the vessel 522 can have any desired orsuitable shape, in this example vessel 522 is cylindrical, and in anycase is configured for preventing the internal volume 526 from beingirradiated by light, as disclosed for the first example, mutatismutandis.

The system 500, in particular the bioreactor 520, further comprises aninfluent inlet (also referred to as waste inlet) 532 (optionallyincluding a valve, not shown, and/or pump 533) at the aerobic bioreactor520 for receiving waste into the internal volume 526 and that is to betreated aerobically by the system 500. The system 500, in particular thebioreactor 520, also comprises a treated effluent outlet 534 with valve531, for dispensing treated effluent that results from aerobicallytreating the waste that is supplied to the aerobic bioreactor 520. Inthis example, the effluent outlet 534 is provided at the aerobicbioreactor 520; in alternative variations of this example the effluentoutlet 534 can instead be provided at oxygen-rich liquid medium source550.

The influent inlet 532 is located at a lower part of the vessel 522, anda plurality of conduits 538 branch out from influent inlet 532 tooverlay the bottom base 523, and are fixed in the vessel 522 in verticalspaced relationship with the bottom base 523. The conduits 538 can bearranged to provide a grid-like pattern, for example, have openings 539that allow influent, at an influent flow rate, to selectively enterinternal volume 526 via influent inlet 532 and conduits 538. In thisexample, the openings 539 are distributed uniformly over the base 523,providing full coverage with respect to the bottom base 523, therebyallowing influent to be evenly distributed over the transverse crosssection of the vessel 522.

The bioreactor 520 further comprises a clarifier vessel 562 located atthe top of the vessel 522 and in fluid communication with the internalvolume 526. The clarifier vessel 562 has a transverse cross-sectionalarea that increases in the upwards direction, and in this example, theclarifier vessel 562 has a frusto-conical outer wall 565 defining aclarifying volume 566. The clarifier vessel 562 has a bottom rim 561that is sealingly fixed to an upper portion 535 of vessel 522 below theupper rim 579 of the vessel 522. A sludge collection channel 537 isformed between the outside of upper portion 535 and the inside offrusto-conical wall 565 (for example having half angle θ of 55°),allowing sludge to accumulate therein, and which can be removedtherefrom. However, in alternative variations of this example, thebottom rim 561 can instead be sealingly fixed directly to the upper rim579 of the vessel 522, for example.

The liquid medium source 550 comprises reservoir 552, for examplesimilar to liquid medium source 150 and reservoir 152 of the firstexample or the liquid medium source and reservoir of the other examplesdisclosed herein or any other suitable configuration, mutatis mutandis,and is configured for providing a supply of liquid medium L that iscontrollably recirculated between the reservoir 552 and the aerobicbioreactor 520.

As with other examples disclosed herein, the reservoir 552 is differentfrom and/or separate from the aerobic bioreactor 520, and defines aninternal volume 556 (for example, of magnitude V2), the respectivereservoir algae growth volume. The internal volume 556 is different fromand separate from the internal volume 526 of the aerobic bioreactor 520,and reservoir 552 is configured for allowing the internal volume 556 tobe irradiated by light.

For example, the reservoir 552 is concentrically defined around theaerobic bioreactor 520, in the form of a horizontal endless loop, forexample an annular raceway, and an upper rim 563 of clarifier 562separates internal volume 556 from the internal volumes 526 and 566. Forexample, a driving device (not shown) is provided for providing motionto the liquid medium L in internal volume 556 of reservoir 552. Forexample, the driving device can comprise a powered paddling devicemounted to the reservoir 552, for example similar to the paddling deviceas disclosed above for other examples, mutatis mutandis.

Optionally, the reservoir 552 comprises suitable mechanical filters,screens or other selective barriers (not shown) at the reservoir outlet,and/or at the reservoir inlet, that prevent passage of the media 190therethrough, while allowing flow of the liquid medium L therethrough.

System 500 comprises a recirculation circuit 580, having a reservoiroutward flow path 581 and a reservoir return flow path 583 for providinga recirculating flow through the aerobic bioreactor 520, and inparticular for recirculating the liquid medium L between the aerobicbioreactor 520 and the reservoir 550, in particular between the internalvolume 526 and the internal volume 556.

The reservoir outward flow path 581 is provided by conduit 584, whichprovides fluid communication, in particular liquid communication,between bioreactor inlet 528 and reservoir outlet 558, and inparticular, to allow flow of liquid from the reservoir 550 to theaerobic bioreactor 520.

The bioreactor inlet 528 is located at a lower part of the vessel 522,and a plurality of conduits 529 branch out from bioreactor inlet 528 tooverlay the base bottom base 523. The conduits 529 are fixed in thevessel 522 in vertical spaced relationship with the base bottom base523. The conduits 529 can be arranged to provide a grid-like pattern,for example, having openings 588 that allow fluid from the reservoir 550to selectively enter internal volume 526 via bioreactor inlet 528 andconduits 529. In this example, the openings 588 are distributeduniformly over the base 523, providing full coverage with respect to thebottom base 523, thereby allowing oxygen, substrates and so on in theliquid medium L to be evenly distributed over the transverse crosssection of the vessel 522.

The reservoir return flow path 583 provides fluid communication, inparticular liquid communication, between bioreactor outlet 527 andreservoir inlet 557, and in particular, to allow flow of liquid mixtureQ from the aerobic bioreactor 520 to the reservoir 550. The liquidmixture Q includes one or more of liquid medium L, waste W, andprocessed effluent E in varying proportions, and the relativeproportions of liquid medium L, waste W, and processed effluent E inliquid mixture Q can be different in different parts of the system 500and/or can vary during operation of the system 500.

In this example, the bioreactor outlet 527 and reservoir inlet 557 aredefined by upper rim 563 of clarifier vessel 562, which functions as aweir allowing liquid from the bioreactor 520 to overflow into thereservoir 550. In alternative variations of this example, reservoirreturn flow path 583 is provided by a conduit which thus provides fluidcommunication, in particular liquid communication, between a suitablebioreactor outlet and a suitable reservoir inlet.

In this example, the recirculation circuit 580 further comprises a pump585 for driving the aforesaid recirculation of the liquid medium Lbetween the aerobic bioreactor 520 and the reservoir 550. For example,such a pump 585 can be similar to pump 185, mutatis mutandis.

Thus, in operation, flow of liquid medium L along the reservoir outwardflow path 581 is via powered pump 585 which forces the flow of liquidmedium L through the bioreactor 520 in a generally upward direction,i.e., in a direction generally opposed to gravity, through the vessel522, while in the reservoir return flow path 583, flow of liquid mediumL is via gravity.

The bioreactor 520 is designed to provide a desired upward flow velocitywithin the vessel 522, for example 3 meters per hour, and to provide asuitable hydraulic retention time (HRT), for example 1 to 2 hours, forthe fluids in the internal volume 526. For a given magnitude V1 of theinternal volume 526, and a given volume flow rate through this volume,the average velocity of the flow through the internal volume 526 can bemodified by changing one or both of the height of the vessel 522 and thetransverse cross-sectional area thereof. For example, the averagevelocity of the flow through the internal volume 526 can be increased,by increasing the height of the vessel 522 and/or decreasing thetransverse cross-sectional area thereof. For example, the averagevelocity of the flow through the internal volume 526 can be decreased,by decreasing the height of the vessel 522 and/or increasing thetransverse cross-sectional area thereof.

As in the other examples disclosed herein, mutatis mutandis, the liquidmedium source 550, in particular the reservoir 552, is configured forgenerating and providing oxygen to liquid medium L, so that theoxygen-rich liquid medium L can be provided to the aerobic bioreactor520 (via conduit 584), and the generation of oxygen is accomplished in asimilar manner, i.e., by the photosynthetic action of photosyntheticmicroorganisms, in particular photosynthetic eukaryotic or prokaryoticmicroorganisms for example algae, (that are carried in the liquid mediumL), when illuminated by said light and provided with appropriatenutrients.

As already mentioned, the aerobic bioreactor 520 is configured foraerobically processing waste using suitable microorganisms and oxygenprovided by oxygen-rich liquid medium L, for example as disclosed hereinfor the first example or other examples, mutatis mutandis.

In this example, the microorganisms are fixed on media 190, as disclosedabove in other examples of the system, mutatis mutandis.

In this example, the media 190 are mobile, i.e. free-floating media,configured for moving within the liquid mixture Q in the internal volume526, the liquid mixture Q including liquid medium L, waste W, andprocessed effluent E in varying proportions during operation of thesystem 500.

In this example, all or a portion (for example a majority) of the media190 have a specific gravity that is greater than that of the liquidmixture Q, or at least of the liquid medium L, for example 1.05 g/ml,and thus in the absence of an upwards flow of liquid within the vessel522, the media 190 would tend to settle at the bottom of the vessel 522.Optionally, some of the media 190 can be provided having a specificgravity that is less than or equal to that of the liquid mixture Q, orat least of the liquid medium L, for example 0.95 g/ml or 1.05 g/ml,respectively, and such media mixes with other media 190 having specificgravity that is greater than that of the liquid mixture Q, or of theliquid medium L, in operation of the aerobic bioreactor 520.

In this example, the free-floating media 190 are prevented from leavingthe aerobic bioreactor 520 and from being transported via recirculationcircuit 580 to the reservoir 552, at least during operation of thesystem 500. For this purpose the aerobic bioreactor 520 can be operatedto provide an upward flow rate and/or upward velocity through the vessel522 sufficiently high on the one hand to have the effect of providing afluidized bed type effect to the media 190, such that the media 190remain generally suspended within the internal volume 526. By generallysuspended is meant that the media 190 can move around within theinternal volume 526, the upward flow rate and/or upward velocity throughthe vessel 522 ensuring that the media 190 take mean positions somewhereintermediate between the bottom base and the top of vessel 522, but onthe other hand the upward flow rate and/or upward velocity through thevessel 522 not being so high such as to cause the media 190, or asignificant portion of the media 190 to maintain mean positions close tothe top of vessel 522, and possibly spill over onto the reservoir 552via the clarifier vessel 562.

The widening cross-section of the clarifier vessel 562 significantlyreduces the velocity of the fluid flowing through the bioreactor 520 atthe clarifier vessel 562, as compared with the flow velocity in thevessel 522. This has the effect of “clarifying” the fluid, i.e.,allowing separation of the media 190, as well as other solids, that cannow flow downwards in the vessel 522.

A suitable filter (not shown), such as for example a rotating clothfilter, is provided to separate the effluent from the clarifiedeffluent, which can be selectively removed via to treated effluentoutlet 534.

Optionally, the aerobic bioreactor 520 comprises suitable mechanicalfilters, screens or other selective barriers (not shown) at thebioreactor outlet 527, and/or at the bioreactor inlet 528, that preventpassage of the media 190 therethrough, while allowing flow of the liquidmedium L therethrough.

Optionally, the media 190 can also additionally comprise fixed media,i.e., a portion of the media is affixed in situ with respect to thelocation thereof within the internal volume 526, i.e., a portion of themedia is fixed in situ within the bioreactor

In this example, the upward flow through the aerobic bioreactor 520provides mixing of the media 190 within the liquid mixture Q, whileminimizing or preventing damage to the media 190. This arrangement doesaway with the need for a mechanical mixer for the system 500, and canreduce the power requirements of the system 500 significantly. Forexample, some mechanical mixers can consume electrical power at a rateof about 25 W/m³ of the volume being mixed, and such power consumptioncan be saved with the current arrangement, for example. Nevertheless, inalternative variations of this example, the aerobic bioreactor 520further comprises a mixing device, configured for mixing the media 190within the liquid mixture Q, while minimizing or preventing damage tothe media 190, for example including the mixing device as disclosedabove for other examples, mutatis mutandis.

Optionally, the system 500 can further comprise an auxiliary aerationsystem (not shown) configured for selectively providing gaseous oxygenor air to the aerobic bioreactor 520, and/or an auxiliary CO₂ systemconfigured for selectively providing gaseous carbon dioxide orcarbon-dioxide rich air to the liquid source 550, for example asdisclosed for the first example or other examples, mutatis mutandis.

In an alternative variation of the fifth example, and referring to FIG.6, the respective bottom base 523′ is configured for sludge collection,and comprises a conical or frusto-conical wall 565′ (for example at halfangle φ of 55°), allowing sludge to accumulate therein, and which can beremoved therefrom via conduit and pump 560′. Thus, solids which settlebelow the conduits 528, 538, in the feed cycle and/or in thesedimentation stage, can be collected in bottom base 523′ and removedtherefrom as desired.

When only influent is flowing into the vessel 522 (with no recirculationflow via recirculation circuit 580), the media 190 are embedded orengulfed in an environment that is low in dissolved oxygen (DO), andhigh in biochemical oxygen demand (BOD). Filtered chemical oxygen demand(CODf) uptake occurs in anaerobic conditions. The media 190 becomessaturated in organic material quantified as chemical oxygen demand (COD)as diffusion resistance is reduced to the existing high concentrationgradient in the vessel 522. On the other hand, when recirculation flowis provided to the aerobic bioreactor 520 via recirculation circuit 580,for example at flow rates between 400% and 600% of the influent flowrate, this provides high dissolved oxygen concentrations anddramatically dilutes COD levels, allowing the media 190 to be exposed toaerobic conditions, and thereby significantly improves the efficiency ofthe aerobic bioreactor 520.

It is to be noted that the aerobic bioreactor 520 can be provided as astand alone unit, that is selectively connectable to any suitable liquidmedium source, for example liquid medium source 550 or any stand aloneliquid medium source, and that is selectively connectable to any sourceof liquid waste.

Operation of system 500 in batch mode (BM), is for example as follows.

Referring to FIGS. 7( a) to 7(c), waste W, mainly in liquid form, isconveyed to the aerobic bioreactor 520 at an effluent flow rate T1 viawaste inlet 532, for a period of time, such that a particular volume ofwaste W is introduced into the vessel 522. For example, such a volume ofwaste W can be sufficient to reach a part of the height of the vessel522, for example to cover media 190, that is mainly suspended in thelower part of the vessel 522.

Optionally, the waste W is first subjected to preprocessing, including ascreening and degritting process to remove solids, with or without apreliminary anaerobic treatment process, prior to being fed to theaerobic bioreactor 520.

If the aerobic bioreactor 520 is already filled up to or close to therim 563, liquid in the upper part of the aerobic bioreactor 520 isdisplaced out of the aerobic bioreactor 520 via the effluent outlet 534.For example, if this batch of waste water W is being processed after thecompletion of processing of a previously batch still in the aerobicbioreactor 520, then effluent E is displaced out of the aerobicbioreactor 520 via the effluent outlet 534 concurrently with a new batchof waste W being introduced into the vessel 522 via waste inlet 532.

The waste input is then turned off at waste inlet 532, and the effluentoutlet 534 is also closed. The liquid medium source 550 is operated toprovide a flow rate of liquid medium L through aerobic bioreactor 520,providing oxygen to the aerobic bioreactor 520, and allowing the aerobicbioreactor 520 and the liquid medium source 550 to each operate underits own optimal conditions, but without continuous addition of waste Wor dispensing of effluent E.

In particular, and referring to FIG. 8, there is provided arecirculating flow of liquid medium L between the reservoir 552 and theaerobic bioreactor 520 via recirculation circuit 580. In practice thereis a recirculating flow of liquid mixture Q, including a high proportionof liquid medium L, between the reservoir 552 and the aerobic bioreactor520 via recirculation circuit 580, at a flow rate T2.

For example, flow rate T2 can be 5 or 6 times greater than effluent flowrate T1. In practice the liquid medium L also carries algae to and fromthe reservoir 552 via recirculation circuit 580. The liquid medium L inreservoir 552 is being continuously provided with oxygen generated bythe algae therein as the liquid medium L is exposed to said light andprovided with nutrients, and this oxygen generation process is enhancedby forcing the liquid medium L to flow around reservoir 552 by theaction of a suitable driver. Thus, the liquid medium L delivered to theaerobic bioreactor 520 via conduit 584 is oxygen-rich. At the same time,CO₂ that is produced by bacteria is transferred to the liquid mixture Q,including liquid medium L, providing carbon for algal growth.

The microorganisms fixed in media 190 treat the waste aerobically forexample by digesting or decomposing the waste, using oxygen dissolved inthe liquid medium L delivered from the reservoir 552, thereby convertingthe waste W into processed effluent E.

As the recirculation flow enters the vessel 522 via the bottom partthereof and flows in an upwards direction through the vessel 522 at arelatively high velocity, the media 190, in particular the media that isheavier than the density of the upflowing liquid mixture Q, becomefluidized and become well mixed in the upflowing liquid mixture Q,enhancing the aerobic processing of the waste W. As the recirculationflow reaches the upper part of the vessel 522 and then through theclarifier vessel 561 of waste W, the flow velocity is significantlyreduced. This essentially results in the media 190 remaining the vessel522 and providing a clarified essentially media free liquid mixture Q inthe clarifier vessel 561. Concurrently, solids and other sludge cancollect at the sludge collection channel 537, and recirculating flowoverflows from rim 563 into the reservoir 552.

In practice, a particular mixture M1 of the processed effluent E,(partially de-oxygenized) liquid medium L, and possibly waste W, invarying proportions, in the liquid mixture Q leaves the aerobicbioreactor 520 via conduit 582. Similarly, a mixture M2 of the processedeffluent E, (oxygen-rich) liquid medium L, and possibly waste W, invarying proportions, of liquid mixture Q recirculates back and entersthe aerobic bioreactor 520 via conduit 584.

Recirculation of liquid mixture Q via recirculation circuit 580continues for a number of recirculation cycles, or for as long asdesired. Typically, when all or most of the waste is processed, theprocessed effluent can be drained from the aerobic bioreactor 520through the effluent outlet 534, though in practice such effluent can bemixed in with a proportion of liquid medium L, and/or possibly with aproportion of waste W.

Similarly, in practice, a particular mixture M3 of the processedeffluent E, liquid medium L, and possibly waste W, in varyingproportions, of liquid mixture Q can be dispensed via the dispensingoutlet 534.

Thus, in operation of the system 500, and as with other examplesdisclosed above, mutatis mutandis, the microorganisms aerobically treatthe waste W in internal volume 526 and in the absence of said light,i.e., in darkened conditions, which are optimal for the microorganisms,while being provided with ample oxygen dissolved in the liquid medium L.In the darkened conditions provided by the aerobic bioreactor 520, thealgae that can be recirculating through the aerobic bioreactor 520 arethus under conditions that do not promote further growth, and thusminimize interference with the aerobic processing of the waste by themicroorganisms. Furthermore, the provision of the microorganism as abiofilm fixed on media 190, in which the microorganism are exposed tothe waste W and oxygen-rich liquid medium L over a large surface arearelative to the volume occupied by the media 190, enables the waste W tobe processed faster and more efficiently than would be the case if themicroorganism were instead provided as a sludge moving throughout thesystem, for example. Furthermore, by creating fluidized bed-typeconditions for the media 190 energy requirements for mixing the mediacan be reduced or eliminated, while concurrently providing efficientmixing of the media with the oxygen rich liquid, and optimizingconditions for aerobic processing of the waste, as compared with notproviding fluidized bed conditions for the media 190. The energyrequirements for operating the system 500 are thus relatively modest.Optionally, however, a mechanical mixer can be selectively used asdesired to further improve mixing, at an energy cost.

On the other hand, the conditions for generating oxygen by the algae insource 550 are also concurrently optimal, the algae receiving said lightand nutrients in the reservoir 552, and preferably kept in motion aroundthe reservoir 552. Further, these conditions are further optimized bythe relative absence of the microorganisms in the reservoir 552, sincethe microorganisms, being fixed on the media 190, are prevented frombeing transported to the reservoir 552 from the aerobic bioreactor 520.

Thus, the aerobic treatment process of waste is independent andseparated from the process of generating oxygen via algae, avoiding orminimizing interference between the two processes, and each process canbe separately and independently optimized.

For a given requirement of throughput of waste through the aerobicbioreactor 520, the reservoir 552 can be sized accordingly whereby toprovide the necessary oxygen demand for the bioreactor 520.

The system 500 can optionally further comprise post-processing systemsfor post-processing the effluent E. For example, downstream of effluentoutlet 134 can be provided further filters and purifiers to furtherpurify the effluent E. For example, a plurality of systems 100 can beconnected in series, with the first one receiving waste W, and havingits effluent outlet 534 connected to the waste inlet 532 of the nextsystem 500 (thus the effluent from the first system is considered as the“waste” being supplied to the next system), which is similarly connectedto the next system, and so on, the last system 100 then dispensing themany-times processed effluent E.

It is to be noted that the aerobic processing of the waste in theaerobic bioreactor 520 generates CO₂ as a byproduct, and this CO₂ can berouted to the reservoir 552 (via suitable piping or the existing liquidflows, for example) to provide additional carbon to the algae therein.Alternatively, the biogas itself, which is rich in CO₂, can be used toenrich the algae with a carbon source by injecting it through the liquidmedium L. Thus, the waste processing system 500 and the correspondingwaste processing method can be considered to be concurrently, oralternatively, a system and method, respectively, for the production ofalgae, in which the algae can be harvested from the respective source ofoxygen-rich liquid medium, and the bioreactor generates the carbonnecessary for the algal growth.

It is also to be noted that in the aforementioned preprocessing in theform of said anaerobic treatment process, biogas can be generated. Thisbiogas can be sold off, or can be utilized for power generation, forexample for powering the system 500, and the CO₂ produced as a byproductof said power generation can also be routed to the reservoir 152 viasuitable piping for example to provide additional nutrients to the algaetherein.

Once a batch of effluent is ready to be removed from the system, a newbatch of waste W can be provided to the system 500 for processing.

Referring to FIG. 9, the system 500 can be operated according to asettle cycle when desired. No waste is provided at waste inlet 532, andno effluent is removed via the effluent outlet 534. Furthermore, thereis no recirculation flow provided by the recirculation circuit 580.Under these conditions, solids in the liquid medium settle below theconduits 538 and 529, and can be removed, for example with thearrangement illustrated in FIG. 6. It is to be noted that a suitablemechanical arrangement, for example a mesh, can be provided in thevicinity of the conduits 538 and 529, for example just above theconduits 538 and 529, to prevent the media 190 from settling at thebottom of the vessel 522 with other unwanted solids.

Alternatively, system 500 can be operated in a continuous flow mode(CFM), for example as follows. Waste W (after the aforesaidpreprocessing) is provided to the aerobic bioreactor 520 continuously,and the recirculation circuit continually provides recirculation flow.The microorganisms that are fixed on media 190 aerobically process thewaste in a similar to that of the BM disclosed above, mutatis mutandis,typically by digesting or decomposing the waste, and the processedeffluent can be drained from the aerobic bioreactor 520 (or optionallyvia the reservoir 552) in a continuous manner. Similar to the CFM modefor the first example disclosed above, mutatis mutandis, the system 500is also set up such that in steady-state operating conditions, mixtureM1 of the liquid mixture Q (i.e., of the processed effluent E,(partially de-oxygenized) liquid medium L, and possibly waste W, thatleaves the aerobic bioreactor 520 via conduit 582) has a high proportionof effluent E relative to waste W, mixture M2 (of the processed effluentE, (oxygen-rich) liquid medium L, and possibly waste W, that circulatesback and enters the aerobic bioreactor 520 via conduit 584) has a highproportion of liquid medium L relative to waste W or effluent E, andmixture M3 of the liquid mixture Q (i.e., of the processed effluent E,liquid medium L, and possibly waste W, that is dispensed via thedispensing outlet 534) has a high proportion of effluent E relative towaste W.

Referring to FIG. 10, the aerobic bioreactor 520 can optionally bemodified as follows. One or more draft tubes 570 are provided in thevessel 522. Each draft tube 570 is laterally spaced from the lateralwalls 524 of the vessel 522, and each said draft tube 570 provides aninitially decreasing flow area in the direction of flow therethrough.For example, each draft tube 570 comprises an inlet flared portion,joined to an exit flared portion via a linear portion. The inlet flaredportion is in the form of an inlet funnel 572 having an inlet rim 572 aand a throat 572 b, the inlet rim 572 a defining a largercross-sectional inlet area than the throat 572 b. The outlet flaredportion is in the form of an outlet funnel 574 having an outlet rim 574a and a throat 574 b, the outlet rim 574 a defining a largercross-sectional inlet area than the throat 574 b. the linear portion isin the form of a generally vertical cylindrical tube 573 joined at alower end thereof to throat 572 b, and at an upper end thereof to throat574 b. Furthermore, the bioreactor inlet 528 is located at a lower partof the vessel 522, and the plurality of conduits 529 branch out frombioreactor inlet 528 to overlay the base bottom base 523, and are fixedin the vessel 522 in vertical spaced relationship with the base bottombase 523. The conduits 529 can be arranged to provide a grid-likepattern, for example, having openings 588 that allow fluid from thereservoir 552 to selectively enter internal volume 526 via bioreactorinlet 528 and conduits 529. However, in the example of FIG. 10, theopenings 588 are distributed uniformly over parts of the base 523 suchthat they are facing a respective inlet funnel 572, thereby facilitatingoxygen, substrates and so on in the liquid medium Q, in particular inthe liquid medium L, to be channeled through the draft tubes 570. Inoperation of the recirculation circuit 580, fluid recirculated viarecirculation circuit 580 and provided to the vessel 522 via theopenings 588 is channeled through draft tubes 570 at a relatively highervelocity than in the absence of the draft tubes 570, further enhancingmixing of the media 190, and furthermore, a recirculation flow field Cis set up within the vessel 520, with liquid flowing in a downwarddirection B within the vessel 522 on the outside of the draft tubes 570.Optionally, but not necessarily, the openings 539 are also distributeduniformly over parts of the base 523 such that they are facing arespective inlet funnel 572, thereby facilitating waste W to bechanneled therefrom through the draft tubes 570. The modified bioreactor520 of FIG. 10 can be operated in batch mode or continuous flow mode ina similar manner to that disclosed above with respect to FIGS. 7( a) to9, mutatis mutandis.

Referring to FIG. 11, the aerobic bioreactor 520 of FIGS. 5( a) to 9 canoptionally be modified as follows. One or more draft tubes 570 areprovided in the vessel 522, similar to the draft tubes of FIG. 10, butinverted, such that the inlet flared portion is now vertically above theexit flared portion. Thus, inlet funnel 572 is now above the generallyvertical cylindrical tube 573, while the outlet funnel 574 is now abovethe generally vertical cylindrical tube 573. Furthermore, the bioreactorinlet 528 is now located at an upper part of the vessel 522, above thedraft tubes 570, and the plurality of conduits 529 that branch out frombioreactor inlet 528 are fixed in the vessel 522 in vertical spacedrelationship with the base bottom base 523, but close to the upper rim579. The conduits 529 are arranged to provide a grid-like pattern, forexample, with openings 588 that allow fluid from the reservoir 552 toselectively enter internal volume 526 via bioreactor inlet 528 andconduits 529. However, in the example of FIG. 11, the openings 588 arefacing a respective inlet funnel 572, thereby facilitating oxygen,substrates and so on in the liquid medium L to be channeled through thedraft tubes 570, but in a downward direction. In operation of therespective recirculation circuit 580, fluid recirculated viarecirculation circuit 580 and provided to the vessel 522 via theopenings 588 is channeled in a downwards direction through draft tubes570, and also at a relatively higher velocity than in the absence of thedraft tubes 570. In this example, at least a portion of the media 190,for a example a majority of or all the media 190, have a specificgravity that is less than that of the liquid mixture Q, or at least ofthe liquid medium L, for example 0.95 g/ml, and such media can be mixedwith other media 190 having specific gravity that is greater than orequal to that of the liquid mixture Q, or of the liquid medium L, forexample 1.05 g/ml or 1.0 g/ml, respectively, in operation of the aerobicbioreactor 520 of FIG. 11. This arrangement also enhances mixing of themedia 190, and furthermore, a recirculation flow field C′ is set upwithin the vessel 520, with liquid flowing in an upward direction B′within the vessel 522 on the outside of the draft tubes 570. Thus, themedia 190 that have a density less than that of the liquid mixture Q, orat least of the liquid medium L, tend to float upwards along directionB′ and re-enter the draft tubes 570 via the upper inlet flared portiondue to the recirculation flow field C′.

In the example of FIG. 11, the influent inlet 532 is now located at anupper part of the vessel 522, above the draft tubes 570, and theplurality of conduits 538 branch out from influent inlet 532 are fixedin the vessel 522 in vertical spaced relationship with the base bottombase 523, but close to the upper rim 579. The conduits 538 are arrangedto provide a grid-like pattern, for example, with openings 539 thatallow influent to selectively enter internal volume 526 via influentinlet 532 and conduits 538. Furthermore, in the example of FIG. 11, theopenings 539 are facing a respective inlet funnel 572, therebyfacilitating the waste W to be channeled through the draft tubes 570, ina downward direction. It is to be noted that is the example of FIG. 11is to be run in batch mode only, and not in continuous flow mode, theinfluent inlet 532, conduits 538 and openings 539 can be arranged asdisclosed for the examples illustrated in FIGS. 5( a) to 10, mutatismutandis, below the draft tubes 570. The modified bioreactor 520 of FIG.11 shows the treated effluent outlet 534 (with valve 531) provided atthe vessel 522, and the portion of the treated effluent outlet 534 thatprojects into internal volume 526 can comprise a discharge screen, forexample.

The modified bioreactor 520 of FIG. 11 can be operated in batch mode orcontinuous flow mode in a similar manner to the batch mode BM orcontinuous flow mode CFM, respectively, as disclosed above with respectto FIGS. 7( a) to 10, mutatis mutandis, with some main differences asfollows. In batch mode or in continuous flow mode, the liquid providedby the recirculation circuit 580 now provides a generally downward flowthrough the draft tubes 570, and effluent is collected from the regionbetween the outside of draft tubes 570 and the lateral walls 524. Incontinuous flow mode the waste influent W is also provided to theinternal volume, in particular towards the draft tubes 570, in adownwards direction therethrough. In batch mode the waste influent W isalso provided to the internal volume, in any direction, for example inan upwards or a downwards direction therethrough.

It is to be noted that the feature of providing a fluidized bedconditions in the system according to the examples of FIG. 5( a) throughto FIG. 11, can be applied in a similar manner, mutatis mutandis, to oneor more of the systems according to the examples illustrated in FIGS. 1to 4.

In the method claims that follow, alphanumeric characters and Romannumerals used to designate claim steps are provided for convenience onlyand do not imply any particular order of performing the steps.

Finally, it should be noted that the word “comprising” as usedthroughout the appended claims is to be interpreted to mean “includingbut not limited to”.

While there has been shown and disclosed examples in accordance with thepresently disclosed subject matter, it will be appreciated that manychanges may be made therein without departing from the spirit of thepresently disclosed subject matter.

1. System for aerobically processing waste, comprising: an aerobicbioreactor configured for aerobically processing waste via bacteriafixed on media to provide processed effluent from the waste; a source ofoxygen-rich liquid medium, said source being different from said aerobicbioreactor, said source being in selective fluid communication with saidaerobic bioreactor.
 2. System according to claim 1, comprising arecirculation circuit configured for controllably recirculating saidliquid medium between said aerobic bioreactor and said source.
 3. Systemaccording to claim 1 or claim 2, wherein said system is configured forpreventing the media from being transferred from the aerobic bioreactorto said source.
 4. System according to any one of claims 1 to 3, whereinsaid media is restricted to a confined volume within said aerobicbioreactor.
 5. System according to any one of claims 1 to 4, wherein inoperation of the system a flow of said oxygen-rich liquid medium isforced through said confined volume wherein to interact with saidbacteria.
 6. System for aerobically processing waste, comprising: anaerobic bioreactor configured for aerobically processing waste toprovide processed effluent from the waste; a source of oxygen-richliquid medium, said source being different from the bioreactor, arecirculation circuit configured for controllably recirculating saidliquid medium between said aerobic bioreactor and said source.
 7. Systemaccording to claim 6, wherein said aerobic bioreactor is configured foraerobically processing waste via bacteria fixed on media.
 8. Systemaccording to claim 7, wherein said system is configured for preventingthe media from being transferred from the aerobic bioreactor to thesource.
 9. System according to any one of claims 7 to 8, wherein saidmedia is restricted to a confined volume within said aerobic bioreactor.10. System according to claim 9, wherein in operation of the system aflow of said oxygen-rich liquid medium is forced through said confinedvolume wherein to interact with said bacteria.
 11. System foraerobically processing waste, comprising: bacteria for aerobicallyprocessing waste to provide processed effluent from the waste, saidbacteria being fixed on media restricted to a confined volume; a flow ofoxygen-rich liquid medium forced through said confined volume wherein tointeract with said bacteria.
 12. System according to claim 11, whereinsaid confined volume is provided in an aerobic bioreactor, and wherein asource of oxygen-rich liquid medium provides said flow of oxygen-richmedium, said source being different from the aerobic bioreactor. 13.System according to claim 12, wherein said system is configured forpreventing the media from being transferred from the aerobic bioreactorto the source.
 14. System according to claim 12 or claim 13, comprisinga recirculation circuit configured for controllably recirculating saidliquid medium between said aerobic bioreactor and said source. 15.System according to any one of claims 1 to 14, wherein said sourcecomprises photosynthetic microorganisms that generate oxygen to saidliquid medium responsive to exposure to light.
 16. System according toany one of claims 1 to 15, wherein said source comprises any one ofphotosynthetic eukaryotic microorganisms and photosynthetic prokaryoticmicroorganisms that generate oxygen to said liquid medium responsive toexposure to light.
 17. System according to any one of claims 1 to 16,wherein said source comprises algae that generate oxygen to said liquidmedium responsive to exposure to light.
 18. System according to any oneof claims 15 to 17, wherein said photosynthetic microorganisms compriseat least one of: Chlorella spp, spirulina, scendesmus, or any otherphotosynthetic microalgae or cyanobacteria.
 19. System according to anyone of claims 1 to 18, wherein said source comprises a reservoircomprising a channel therein defining a reservoir internal volume, andconfigured for driving said liquid medium around said channel inoperation of the system.
 20. System according to any one of claims 1 to19, further comprising an auxiliary aeration system, configured forselectively providing gaseous oxygen or air to said bioreactor. 21.System according to any one of claims 1 to 20, further comprising anauxiliary CO₂ system, configured for selectively providing carbondioxide to said source.
 22. System according to any one of claims 1 to21, wherein said media is fixed in situ within the bioreactor. 23.System according to any one of claims 1 to 22, wherein said media ismobile within the bioreactor.
 24. System according to any one of claims1 to 23, wherein said media comprise biofilm carrier elements, in theform of solid inert substrates having a relatively large surface area tovolume ratio.
 25. System according to any one of claims 1 to 24,comprising a waste inlet configured for receiving the waste and adispensing outlet for dispensing treated effluent, and wherein saidbioreactor comprises at least one vessel defining a respective aerobicprocessing volume, the at least one vessel comprising a bioreactor fluidmedium inlet and a bioreactor fluid medium outlet, each in selectivefluid communication with said source, the at least one vessel beingconfigured for ensuring that the respective aerobic processing volume ispartially or fully shielded from light at least during operation of thesystem; said source comprises at least one reservoir defining arespective reservoir volume for accommodating a volume of said liquidmedium, and further comprising a source fluid medium inlet and a sourcefluid medium outlet, each in selective fluid communication with saidaerobic bioreactor, and a driving device for providing motion to saidliquid medium within said respective reservoir volume, the at least onereservoir being configured for ensuring that the respective reservoirvolume is exposed to light at least during operation of said sourcewherein to provide said oxygen-rich liquid medium.
 26. System accordingto claim 25, wherein said driving device comprises a powered paddlingdevice mounted to the respective said reservoir.
 27. System according toclaim 25 or claim 26, wherein said at least one reservoir comprises atleast one flow channel in the form of a horizontal endless loop. 28.System according to claim 27, wherein said at least one flow channel hasan annular plan form.
 29. System according to claim 27, wherein said atleast one flow channel has a raceway configuration.
 30. System accordingto any one of claims 25 to 29, wherein said source fluid medium outletis configured for preventing outflow of said media therethrough. 31.System according to any one of claims 25 to 30, comprising: at least oneset of conduits providing said fluid communication between said at leastone said vessel and a respective said reservoir; a pumping system,different from said driving device, for providing recirculation of saidmedium between said at least one vessel and the respective saidreservoir through said set of conduits.
 32. System according to claim31, wherein one said conduit connects said source fluid medium inletwith said bioreactor fluid medium outlet and wherein another saidconduit connects said source fluid medium outlet with said bioreactorfluid medium inlet.
 33. System according to any one of claims 1 to 32,wherein said waste is aerobically treatable for removing pollutantstherefrom.
 34. System according to any one of claims 1 to 33, whereinsaid waste is a liquid waste.
 35. System according to any one of claims1 to 34, wherein said waste comprises waste water.
 36. System accordingto any one of claims 1 to 35, wherein said waste includes organic typesof waste.
 37. System according to any one of claims 1 to 36, whereinsaid waste comprises at least one of animal, agricultural, industrial orhuman waste transported in water or another liquid medium.
 38. Systemaccording to any one of claims 1 to 37, wherein said bioreactor isconfigured for providing a through-flow of at least the oxygen-richliquid medium through the bioreactor at a predetermined velocity,wherein said predetermined velocity is sufficient to cause the mediatherein to expand within the bioreactor and to mix therein with at leastthe oxygen-rich liquid medium.
 39. A method for aerobically processingwaste, comprising: aerobically reacting waste in an aerobic bioreactorvia bacteria fixed on media; providing oxygen-rich liquid medium to thebioreactor from an oxygen-rich liquid source, wherein the oxygen-richliquid source is different from the bioreactor.
 40. Method according toclaim 39, further comprising controllably recirculating said liquidmedium between said aerobic bioreactor and said oxygen-rich source. 41.Method according to claim 39 or claim 40, comprising preventing themedia from being transferred from the aerobic bioreactor to said source.42. Method according to any one of claims 39 to 41, wherein said mediais restricted to a confined volume within said aerobic bioreactor. 43.Method according to claim 42, a flow of said oxygen-rich liquid mediumis forced through said confined volume wherein to interact with saidbacteria.
 44. A method for aerobically processing waste, comprising:aerobically processing waste in an aerobic bioreactor to provideprocessed effluent from the waste; providing oxygen-rich liquid mediumto the bioreactor from an oxygen-rich liquid source, wherein theoxygen-rich liquid source is different from the bioreactor, controllablyrecirculating said liquid medium between said aerobic bioreactor andsaid source.
 45. Method according to claim 44, wherein said aerobicbioreactor is configured for aerobically processing waste via bacteriafixed on media.
 46. Method according to claim 45, comprising preventingthe media from being transferred from the aerobic bioreactor to theoxygen-rich liquid source.
 47. Method according to any one of claims 45to 46, wherein said media is restricted to a confined volume within saidaerobic bioreactor.
 48. Method according to claim 47, wherein a flow ofsaid oxygen-rich liquid medium is forced through said confined volumewherein to interact with said bacteria.
 49. A method for aerobicallyprocessing waste, comprising: aerobically processing waste with bacteriato provide processed effluent from the waste, said bacteria being fixedon media restricted to a confined volume; forcing a flow of oxygen-richliquid medium through said confined volume wherein to interact with saidbacteria.
 50. Method according to claim 49, wherein said confined volumeis provided in an aerobic bioreactor, and wherein a source ofoxygen-rich liquid medium provides said flow of oxygen-rich medium, saidsource being different from the aerobic bioreactor.
 51. Method accordingto claim 50, comprising preventing the media from being transferred fromthe aerobic bioreactor to the source.
 52. Method according to claim 50or claim 51, comprising controllably recirculating said liquid mediumbetween said aerobic bioreactor and said source.
 53. Method according toany one of claims 39 to 52, wherein said liquid medium comprisesphotosynthetic microorganisms that generate and provide oxygen to saidliquid medium responsive to exposure to light.
 54. A method foraerobically processing waste, comprising: reacting waste aerobicallywith bacteria in a bioreactor volume under conditions configured forinhibiting or reducing growth of photosynthetic microorganisms;providing a flow of oxygen-producing photosynthetic microorganismsthrough the bioreactor volume from a source configured for promotingoxygen production by photosynthetic microorganisms, the source beingdifferent from the bioreactor volume, the photosynthetic microorganismsgenerating and providing oxygen to said liquid medium responsive toexposure to light; and preventing at least a majority of the bacteriafrom exiting the bioreactor with said flow of photosyntheticmicroorganisms.
 55. Method according to any one of claims 53 to 54,wherein said photosynthetic microorganisms comprise any one ofphotosynthetic eukaryotic microorganisms and photosynthetic prokaryoticmicroorganisms that generate oxygen to said liquid medium responsive toexposure to light.
 56. Method according to any one of claims 53 to 55,wherein said source comprises algae that generate oxygen to said liquidmedium responsive to exposure to light.
 57. Method according to any oneof claims 53 to 56, wherein said photosynthetic microorganisms compriseat least one of: Chlorella spp., spirulina, scendesmus, or any otherphotosynthetic microalgae or cyanobacteria.
 58. Method according to anyone of claims 39 to 57, wherein said waste is aerobically treatable forremoving pollutants therefrom.
 59. Method according to any one of claims39 to 58, wherein said waste is a liquid waste.
 60. Method according toany one of claims 39 to 59, wherein said waste comprises waste waterand/or organic types of waste.
 61. Method according to any one of claims39 to 60, wherein said waste comprises at least one of animal,agricultural, industrial or human waste transported in water or anotherliquid medium.
 62. Method according to any one of claims 39 to 61,further comprising at least one of: selectively providing gaseous oxygenor air to said bioreactor; and selectively providing carbon dioxide tosaid source.
 63. Method according to any one of claims 39 to 62, whereina portion of said media is fixed in situ within the bioreactor. 64.Method according to any one of claims 39 to 63, wherein at least aportion of said media is mobile within the bioreactor.
 65. Methodaccording to any one of claims 39 to 64, wherein said media comprisebiofilm carrier elements, in the form of solid inert substrates having arelatively large surface area to volume ratio.
 66. Method according toany one of claims 39 to 65, comprising: partially or fully shielding therespective aerobic processing volume from light; ensuring that therespective reservoir volume is exposed to light.
 67. Method according toany one of claims 39 to 66, wherein step of aerobically reacting wasteincludes providing a through-flow of at least the oxygen-rich liquidmedium through the bioreactor at a predetermined velocity, wherein saidpredetermined velocity is sufficient to cause the media therein toexpand and to mix therein with at least the oxygen-rich liquid medium.68. Method according to any one of claims 39 to 67, wherein said methodis performed in batch mode.
 69. Method according to any one of claims 39to 67, wherein said method is performed in continuous flow mode. 70.Aerobic bioreactor configured for aerobically processing waste viabacteria fixed on media that are mobile within the aerobic bioreactor toprovide processed effluent from the waste, comprising: a reaction vesselhaving a fluid inlet and a fluid outlet, and a waste inlet, and definingan internal volume; said waste inlet being configured for selectivelyproviding waste to said aerobic bioreactor; said fluid inlet and saidfluid outlet being connectable to a source of oxygen-rich liquid medium,the source being different from said aerobic bioreactor, wherein saidsource is in selective fluid communication with said aerobic bioreactorvia said fluid inlet and said fluid outlet to provide a recirculationcircuit configured for controllably recirculating at least the liquidmedium between said aerobic bioreactor and the source; the reactionvessel being configured for providing, via said recirculation circuit, athrough-flow of at least the oxygen-rich liquid medium through saidinternal volume at a predetermined velocity, wherein said predeterminedvelocity is sufficient to cause the media to expand within the reactionvessel and mix therein with at least the oxygen-rich liquid medium. 71.Aerobic bioreactor according to claim 70, wherein said predeterminedvelocity is sufficient to provide a fluidized bed effect to the mediawithin said reaction vessel.
 72. Aerobic bioreactor according to claim70 or claim 71, wherein at said predetermined velocity is sufficient toprovide upward motion to at least a first proportion of said mediahaving a density greater than that of said liquid medium.
 73. Aerobicbioreactor according to claim 72, wherein said flow velocity within saidreaction vessel is in a direction generally opposed to the gravitationalgradient.
 74. Aerobic bioreactor according to claim 73, wherein saidfirst proportion is a majority of the total amount of said media in saidreaction vessel.
 75. Aerobic bioreactor according to any one of claims72 to 74, wherein said fluid inlet is provided at a lower part of thereaction vessel and said fluid outlet is provided at an upper part ofthe reaction vessel.
 76. Aerobic bioreactor according to any one ofclaims 72 to 75, wherein said fluid inlet comprises a plurality ofopenings within said reaction vessel, and wherein said openings aredistributed over a bottom base of the reaction vessel providing adesired coverage with respect to the bottom base.
 77. Aerobic bioreactoraccording to claim 76, wherein said openings are uniformly distributedover a bottom base of the reaction vessel providing a full coverage withrespect to the bottom base.
 78. Aerobic bioreactor according to any oneof claims 72 to 77, wherein said reaction vessel comprises one or moredraft tubes, each draft tube being configured to further increase saidfluid velocity therein.
 79. Aerobic bioreactor according to claim 78,wherein each said draft tube provides an initially decreasing flow areain the direction of flow therethrough.
 80. Aerobic bioreactor accordingto claim 78 or claim 79, wherein said openings of said fluid inlet areuniformly distributed over a part of bottom base of the reaction vesselopposite said draft tubes providing a full coverage with respect to thedraft tubes.
 81. Aerobic bioreactor according to claim 70 or claim 71,wherein at said predetermined velocity is sufficient to provide downwardmotion to said media having a density less than that of said liquidmedium.
 82. Aerobic bioreactor according to claim 81, wherein said flowvelocity within said reaction vessel is in at least partially alignedwith the gravitational gradient, and wherein at least a secondproportion of said media has a density less than that of said liquidmedium.
 83. Aerobic bioreactor according to claim 82, wherein saidsecond proportion is a majority of the total amount of said media insaid reaction vessel.
 84. Aerobic bioreactor according to any one ofclaims 81 to 83, wherein said fluid inlet is provided at an upper partof the reaction vessel.
 85. Aerobic bioreactor according to any one ofclaims 81 to 84, wherein said reaction vessel comprises one or moredraft tubes, each draft tube being configured to further increase saidfluid velocity therein.
 86. Aerobic bioreactor according to claim 85,wherein said openings of said fluid inlet are uniformly distributed overan upper opening of each said draft tubes providing a full coverage withrespect to the draft tubes.
 87. Aerobic bioreactor according to claim86, wherein each said draft tube provides an initially decreasing flowarea in the direction of flow therethrough.
 88. Aerobic bioreactoraccording to any one of claims 70 to 87, further comprising a firstsludge receiving receptacle at a lower part thereof for receiving anddisposing of sludge from the aerobic bioreactor.
 89. Aerobic bioreactoraccording to any one of claims 70 to 88, further comprising a clarifyingvessel on an upper part of said reaction vessel and in fluidcommunication therewith, wherein said fluid outlet is provided on saidclarifying vessel, and wherein said clarifying vessel is configured forreducing said fluid velocity therein.
 90. Aerobic bioreactor accordingto claim 89, wherein said clarifying vessel comprises a cross-sectionalarea that increases in an upward direction.
 91. Aerobic bioreactoraccording to claim 89 or claim 90, wherein said clarifying vesselcomprises a second sludge receiving receptacle at a lower part thereoffor receiving and disposing of sludge from the clarifying vessel. 92.Aerobic bioreactor according to any one of claims 70 to 91, furthercomprising an effluent outlet for removing processed effluent from saidaerobic bioreactor.
 93. A system for processing waste, comprising: anaerobic bioreactor as defined in any one of claims 70 to 92; the sourceof oxygen-rich liquid medium as defined in any one of claims 70 to 92,wherein said fluid inlet and said fluid outlet are connected to thesource of oxygen-rich liquid medium; and the media as defined in any oneof claims 70 to 92, and provided in said aerobic bioreactor.
 94. Systemaccording to claim 93, wherein said system is configured for preventingthe media from being transferred from the aerobic bioreactor to saidsource.
 95. System according to any one of claims 93 to 94, wherein saidmedia is restricted to a confined volume within said aerobic bioreactor.96. System according to any one of claims 93 to 95, wherein said sourcecomprises photosynthetic microorganisms that generate oxygen to saidliquid medium responsive to exposure to light.
 97. System according toany one of claims 93 to 96, wherein said source comprises any one ofphotosynthetic eukaryotic microorganisms and photosynthetic prokaryoticmicroorganisms that generate oxygen to said liquid medium responsive toexposure to light.
 98. System according to any one of claims 93 to 97,wherein said source comprises algae that generate oxygen to said liquidmedium responsive to exposure to light.
 99. System according to any oneof claims 96 to 98, wherein said photosynthetic microorganisms compriseat least one of: Chlorella spp, spirulina, scendesmus, or any otherphotosynthetic microalgae or cyanobacteria.
 100. System according to anyone of claims 93 to 99, wherein said source comprises a reservoircomprising a channel therein defining a reservoir internal volume, andconfigured for driving said liquid medium around said channel inoperation of the system.
 101. System according to any one of claims 93to 100, further comprising an auxiliary aeration system, configured forselectively providing gaseous oxygen or air to said bioreactor. 102.System according to any one of claims 93 to 101, further comprising anauxiliary CO₂ system, configured for selectively providing carbondioxide to said source.
 103. System according to any one of claims 93 to102, wherein a portion of said media is fixed in situ within thebioreactor.
 104. System according to any one of claims 93 to 103,wherein said media comprise biofilm carrier elements, in the form ofsolid inert substrates having a relatively large surface area to volumeratio.
 105. System according to any one of claims 93 to 104, comprisinga waste inlet configured for receiving the waste and a dispensing outletfor dispensing treated effluent, and wherein: said internal volume ispartially or fully shielded from light at least during operation of thesystem; said source comprises at least one reservoir defining arespective reservoir volume for accommodating a volume of said liquidmedium, and further comprising a source fluid medium inlet and a sourcefluid medium outlet, each in selective fluid communication with saidaerobic bioreactor, and a driving device for providing motion to saidliquid medium within said respective reservoir volume, the at least onereservoir being configured for ensuring that the respective reservoirvolume is exposed to light at least during operation of said sourcewherein to provide said oxygen-rich liquid medium.
 106. System accordingto claim 105, wherein said driving device comprises a powered paddlingdevice mounted to the respective said reservoir.
 107. System accordingto claim 105 or claim 106, wherein said at least one reservoir comprisesat least one flow channel in the form of a horizontal endless loop. 108.System according to claim 107, wherein said at least one flow channelhas an annular plan form.
 109. System according to any one of claims 105to 108, wherein said source fluid medium outlet is configured forpreventing outflow of said media therethrough.
 110. System according toany one of claims 105 to 108, comprising: at least one set of conduitsproviding said fluid communication between said at least one said vesseland a respective said reservoir; a pumping system, different from saiddriving device, for providing recirculation of said medium between saidat least one vessel and the respective said reservoir through said setof conduits.
 111. System according to any one of claims 93 to 110,wherein said waste is aerobically treatable for removing pollutantstherefrom.
 112. System according to any one of claims 93 to 111, whereinsaid waste is a liquid waste.
 113. System according to any one of claims93 to 112, wherein said waste comprises at least one of waste water;organic types of waste; at least one of animal, agricultural, industrialor human waste transported in water or another liquid medium.